Moscow signaled Tuesday that it will not oppose to Ukraine's membership in European Union, as the "topic is not in line with strategic security issues."

Kremlin spokesperson Dmitry Peskov said Tuesday that Ukraine's application to join the EU "lies on a different plane," because the EU is not a military-political bloc (unlike NATO) and Kyiv's desire to join the EU is fixed in the Constitution of Ukraine.

"Kyiv's potential accession to the European Union is not a military-political bloc, so this topic is not in line with strategic security issues," he said during press conference in Moscow.

He also noted that Kremlin continues to consider Volodymyr Zelenskyy as president of Ukraine. In addition, Peskov was asked if Russia would somehow participate in Ukrainian elections in the future.

"The Kremlin cannot participate in elections in Ukraine. This is a different country," Peskov replied.

Zelenskyy on Monday said he had signed an official request for his country to join the European Union. He posted photos of himself signing the application and his office said the paperwork was on its way to Brussels, where the 27-nation European Union is headquartered. The announcement came after the president urged the bloc to grant his country immediate membership under a special procedure, as Russia's assault against the pro-Western country entered its fifth day.

"We appeal to the European Union for the immediate accession of Ukraine via a new special procedure," the 44-year-old leader said in a video address earlier on Monday. "Our goal is to be together with all Europeans and, most importantly, to be on an equal footing. I'm sure it's fair. I'm sure it's possible."

During his video address, he also urged Russian soldiers to lay down their weapons and leave as Ukrainian and Russian delegations held talks on Moscow's invasion.

Russian shelling pounded the central square in Ukraine's second-largest city and other civilian targets Tuesday and a 40-mile convoy of tanks and other vehicles threatened the capital – as Ukraine's embattled president accused Moscow of resorting to terror tactics to press Europe's largest ground war in generations.

With the Kremlin increasingly isolated by tough economic sanctions that have tanked the ruble currency, Russian troops advanced on Ukraine's two biggest cities. In strategic Kharkiv, an eastern city with a population of about 1.5 million, videos posted online showed explosions hitting the region's Soviet-era administrative building and residential areas. A maternity ward relocated to a shelter amid shelling.

Zelenskyy called the attack on Kharkiv's main square "frank, undisguised terror," blaming a Russian missile and calling it a war crime. "Nobody will forgive. Nobody will forget.... This is state terrorism of the Russian Federation."

As the fighting reached beyond military targets on Day 6 of a Russian invasion that has shaken the 21st century world order, reports emerged that Moscow has used cluster bombs on three populated areas. If confirmed, that would mean the war has reached a worrying new level.

The Kremlin denied Tuesday that it has used such munitions and insisted again that its forces only have struck military targets – despite evidence documented by The Associated Press (AP) reporters of shelling of homes, schools and hospitals.

Russian Defense Minister Sergei Shoigu vowed Tuesday to press the offensive until it achieves its goals, after a first round of talks between Ukraine and Russia yielded no stop in the fighting. Both sides agreed to another meeting in coming days.