More than 4,500 alleged war crimes are now being investigated by Ukrainian prosecutors after appalling reports of atrocities committed in the Ukrainian town of Bucha came to the spotlight, triggering international condemnations and a wave of accusations against Russian troops.

As of Tuesday, there were 4,468 potential war crimes under investigation, according to figures released by the prosecutor's office, and that number is rising by the hundreds every day. The agency estimates that 167 children also died as a result of the Russian military actions in Ukraine.

During the press briefing held from Bucha on Tuesday, Ukraine’s prosecutor general Iryna Venediktova described the recently liberated towns surrounding Kyiv as a "tortured region from hell" and pledged to "punish the inhumans who set it up on our land."

"Russia will be responsible for Bucha in The Hague," she said in a statement on Tuesday. "Prosecutors and investigators are already examining the area (Kyiv region) and documenting crimes, so that every perpetrator of these atrocities are brought to justice both in national and international courts," she said.

Pretrial investigations have begun across the country, including in the Kyiv, Kharkiv, Sumy, Mykolaiv, Donetsk and Luhansk regions, Ukraine’s prosecutor's office asserted.

"We are collecting evidence for the national courts and the International Criminal Court (ICC) in the Hague. Evidence is no longer just war crimes, but crimes against humanity. And we will prove every fact to punish those who tortured, mocked and destroyed Ukrainians," Venediktova said.

The calls for war crimes investigations and trials have intensified after horrific photographs emerged of corpses on roads and in mass graves in Bucha, near Kyiv, after Russian troops retreated from the devastated town. The Kremlin has denied responsibility and suggested the images are fake or that the deaths occurred after Russian forces pulled out of the area.

A number of countries demanded the probe, including Turkey and China, who called images of civilian deaths in the Ukrainian town of Bucha "deeply disturbing."

China supports all initiatives and measures "conducive to alleviating the humanitarian crisis" in the country, and is "ready to continue to work together with the international community to prevent any harm to civilians," Foreign Ministry spokesperson Zhao Lijian told reporters at a daily briefing.

"The truth and the cause of the incident must be verified," Zhao said. "All parties should exercise restraint and avoid unfounded accusations before a conclusion of the investigation is drawn," he added.

Zhao's remarks echo those of China's Ambassador to the United Nations Zhang Jun who earlier called for an investigation, also describing the reports and images of civilian deaths in Bucha as "deeply disturbing."

"The relevant circumstances and specific causes of the incident should be verified and established," Zhang said in remarks to the Security Council on Tuesday, adding that, "before the full picture is clear, all sides should exercise restraint and avoid unfounded accusations."

Shocking images of bodies strewn in Ukrainian streets clearly indicate war crimes, but legally proving that and ensuring accountability is tricky, according to a top international justice expert. Philip Grant, who heads the TRIAL International nongovernment organization (NGO) that works to ensure accountability for international crimes, said that, while powerful, such images alone cannot legally prove war crimes have occurred and who is responsible.

"Images in themselves rarely count as the defining evidence," he told Agence France-Presse (AFP) in an interview. "They can reveal important elements, but they will not reveal the full story," he said.

Grant said it was important to be "cautious" when interpreting events, pointing to past examples of manipulation and misinterpretation. There was, for instance, the dramatic misreporting that a massacre occurred during the 1989 Timisoara uprising in Romania, and Soviet efforts during the Nuremberg trials to pin its own 1940 Katyn massacre of Polish officers on Nazi Germany.

At the same time, Grant said, investigators should "exercise sound judgment" with what they can see. In the case of the Bucha images, "it looks pretty clear-cut that war crimes have been committed," he said.

But the images alone do not make it possible to "attribute that responsibility to a specific person or to a specific group."

Even if it was determined that "Russians did it," he said, "that's not accountability. We need to know who ordered that," he cautioned.

"Is it (Russian President) Vladimir Putin? Is it the commander on the ground? Is it a rogue unit?" "In terms of criminal liability," he said, "it's too early to say who should end up in court for those crimes," he explained.

That process can be long and complicated, he acknowledged.

As the ICC, the U.N. Human Rights Council and a growing number of countries begin sending war crimes investigators to Ukraine, they will have their work cut out for them, Grant said.

Meanwhile, in an address to Irish deputies, Wednesday Ukrainian President Volodymyr Zelenskyy has accused Russia of using hunger as a weapon of war by deliberately targeting Ukraine’s essential food supplies. Zelenskyy said Russian forces "are destroying things that are sustaining livelihoods" including food storage depots, blocking ports so Ukraine could not export food and "putting mines into the fields."

"For them, hunger is also a weapon, a weapon against us ordinary people," he said, accusing Russia of "deliberately provoking a food crisis" in Ukraine, a major global producer of staples including wheat and sunflower oil.

He said it would have international ramifications, because "there will be a shortage of food and the prices will go up, and this is reality for the millions of people who are hungry, and it will be more difficult for them to feed their families."

Zelenskyy spoke by video to a joint session of Ireland’s two houses of parliament, the latest in a string of international addresses he has used to rally support for Ukraine.

British defense officials say 160,000 people remain trapped in the besieged city of Mariupol, where Russian airstrikes and heavy fighting are continuing.

The Ministry of Defense said in an intelligence update Wednesday that those in the city have "no light, communication, medicine, heat or water." It accused Russian forces of deliberately preventing humanitarian access, "likely to pressure defenders to surrender."

Repeated attempts by the International Committee of the Red Cross to get a humanitarian convoy into the southern port city have failed. Ukraine’s Deputy Prime Minister Iryna Vereshchuk said Russian forces stopped buses accompanied by Red Cross workers from traveling to Mariupol, which had a pre-war population of about 400,000. She said Russian troops allowed 1,496 civilians to leave the Sea of Azov port on Tuesday.

Ukraine demands tougher sanctions

The Ukrainian president also condemned hesitancy in Europe over barring Russian energy imports, arguing some leaders were more worried about business losses than about war crimes.

New "rhetoric" about sanctions had emerged, he told the Irish parliament, "but I cannot tolerate any indecisiveness after everything we have gone through in Ukraine and everything that Russian troops have done.

"We still need to convince Europe that Russian oil cannot feed the Russian military machine with new sources of funding," Zelenskyy added, calling also for the total exclusion of Russian banks from Western finance. "The only thing we are lacking is the principled approach of some leaders – political leaders, business leaders – who still think that war and war crimes are not as horrific as financial losses," he said, speaking through an interpreter.

The European Union is poised to implement a fifth round of sanctions cutting off Russian coal imports, while NATO and G-7 foreign ministers are gathering in Brussels for further steps on coordinated action. Some EU countries, notably Germany, have been reluctant to hit all Russian energy exports because of the damage it would do to their own economies.

The EU must impose oil and gas sanctions on Russia "sooner or later," European Council chief Charles Michel told members of the European Parliament in Strasbourg.

Zelenskyy detailed incessant Russian attacks on civilian infrastructure in Ukraine including in the devastated city of Mariupol, where he said even melted snow was no longer available for people to use as drinking water.

Elsewhere, Russian forces overnight struck a fuel depot and a factory in Ukraine’s Dnipropetrovsk region, and the number of casualties remains unclear, the region’s Governor Valentyn Reznichenko said Wednesday on the Telegram messaging app.

"The night was alarming and difficult. The enemy attacked our area from the air and hit the oil depot and one of the plants. The oil depot with fuel was destroyed. Rescuers are still putting out the flames at the plant. There is a strong fire," Reznichenko wrote.

In the eastern Luhansk region, Tuesday’s shelling of Rubizhne city killed one and injured five more, Governor Serhiy Haidai said Wednesday on Telegram.

The Russian military continues to focus its efforts on preparing for an offensive in Ukraine’s east, according to a Wednesday morning update by Ukraine’s General Staff, with the aim "to establish complete control over the territory of Donetsk and Luhansk regions."

Parts of the two regions have been under the control of Russia-backed rebels since 2014 and are recognized by Moscow as independent states.

Authorities in Luhansk urged civilians on Wednesday to evacuate "while it is safe," warning that Russian bombardments could cut off escape routes. Vereshchuk said in online comments that Ukraine aimed to open 11 humanitarian corridors on Wednesday to evacuate civilians.

"We will take everyone out if the Russians allow us to get to the meeting places (for evacuation). Because, as you can see, they don't always observe cease-fires," Haidai wrote on the Telegram messaging app. "I appeal to every resident of the Luhansk region – evacuate while it is safe... While there are buses and trains – take this opportunity. "

Haidai said rail connections in the Donetsk region of Donbass had been damaged this week and took several hours to repair.

"This is another alarm bell," he said.

Haidai said separately in a video address that Russian forces had not managed to break through Ukrainian defenses in his region but were destroying "everything in their path" and would "stop at nothing."