Russia "must stop" its blockade of Ukrainian seaports following its withdrawal from the United Nations and Türkiye-brokered deal ensuring grain shipments, European Council president Charles Michel said Friday.

"It's frankly scandalous that Russia, after having terminated the Black Sea grain initiative, is blocking and attacking Ukrainian ports. This must stop," Michel told reporters in India's capital New Delhi ahead of a G-20 summit.

Russia pulled out of the grain agreement in mid-July after claiming that a parallel deal promising to remove obstacles to Russian exports of food and fertilizer hadn't been honored.

Tensions have built in the region since, with Russia mounting attacks on Ukrainian export hubs and Kyiv's forces targeting Moscow's naval ports and warships.

The Kremlin has since asked Türkiye to help Russia export its grain to African countries with no involvement from Ukraine.

President Vladimir Putin said Monday that Moscow is just weeks away from supplying free grain of up to 1 million metric tons to six African countries.

"The Kremlin's offer of one million tons of grain to Africa is absolutely cynical," Michel said.

"Ships with grains need to have safe access to the Black Sea," he said, noting that the U.N. initiative had initially delivered 32 million tons to the market, "especially to developing countries."

Ukraine and Russia are major exporters of grain and seed oil.

Last year's grain agreement helped push down global food prices and provide Ukraine with an important source of revenue to fight the war.

"Over 250 million people face acute food insecurity worldwide, and by deliberately attacking Ukraine's seaports, the Kremlin is depriving them of the food they desperately need," Michel added.

Meanwhile, the Russian president is to skip the G-20 leaders meeting in India, with Foreign Minister Sergei Lavrov taking Putin's place at the summit this weekend.

Relations between Moscow and many members of the bloc remain fraught over the war in Ukraine.

British Prime Minister Rishi Sunak, in a statement released ahead of his travel to India for the meeting, condemned Putin's actions in Ukraine and said London would hold a summit in November focussed on food security and malnutrition.

"Once again, Vladimir Putin is failing to show his face at the G-20. He is the architect of his own diplomatic exile, isolating himself in his presidential palace and blocking out criticism and reality," Sunak said.

Romania upgrades grain infrastructure

NATO-member Romania's government meanwhile was set on Friday to approve a plan to upgrade road infrastructure in the Black Sea port of Constanta, part of wider investments in the port which could help more Ukrainian grain to transit.

Constanta is Ukraine's largest alternative export route, with grains arriving by road, rail, or barge on the Danube.

Ukraine is one of the world's biggest grain exporters and Romanian government officials have said they aimed to double the monthly transit capacity of Ukrainian grain to Constanta to 4 million tonnes in the coming months.

The government has upgraded dozens of railroad lines connecting it to Ukraine, and works are underway on the Danube to enable more barges to pass, including by hiring more pilots and making navigation possible at night.

In Constanta Port, the transport ministry will use European Union funds to repair or reinforce existing infrastructure, build new roads, access ramps and roundabouts, as well as launch a digitized traffic management system, the draft project showed.

"This is clear proof Romania is making serious efforts to support Ukraine by enabling grain transit, but also to interconnect the region," Prime Minister Marcel Ciolacu told a government meeting.

Works in the port, which will cost 721.3 million lei ($155.67 million), are estimated to take 36 months.

Since July, when Moscow abandoned the grain deal, Ukrainian river ports that lie across the Danube from Romania were repeatedly struck.

Ukraine shipped 8.1 million tons of grain through the port of Constanta in the first seven months.

Exports through the port could increase to 35 million metric tons per season if certain changes are made to operations, the head of the Ukrainian Grain Traders Union UGA said.