African leaders pressed Russian President Vladimir Putin on Friday to move ahead with their peace plan to end the Ukraine war and renew a deal on the export of Ukrainian grain that Moscow tore up last week.

While not directly critical of Russia, their interventions on day two of a summit with Putin served as pointed reminders to him of the depth of African concern at the consequences of the war, especially for food prices.

"The African (peace) initiative deserves the closest attention, it mustn't be underestimated," Congo Republic President Denis Sassou Nguesso told Putin and fellow African leaders in St Petersburg.

"We once again urgently call for the restoration of peace in Europe," he said via a translator.

Egyptian President Abdel Fattah al-Sisi urged Russia to revive the Black Sea grain deal which, until Moscow refused to renew it last week, had allowed Ukraine to export grain from its seaports despite the war.

Sisi, whose country is a key buyer of grain via the Black Sea route, told the summit it was "essential to reach agreement" on reviving the deal.

Putin responded by arguing, as he has in the past, that rising world food prices were a consequence of Western policy mistakes that long predated the Ukraine war.

He says Russia quit the Black Sea agreement last week because it was not getting grain to the poorest countries and the West was not keeping its side of the bargain.

Since withdrawing from the deal, Russia has repeatedly bombed Ukrainian ports and grain depots, prompting accusations from Ukraine and the West that it is using food as a weapon of war, and global grain prices have risen again.

Putin is using the St Petersburg summit to try to inject new momentum into Russia's ties with Africa, promising increased trade and investment there as part of a drive to counter what he portrays as a hegemonic US-dominated world order.

On Thursday, he promised to deliver free Russian grain in the next several months to six of the countries attending the summit.

In Friday's remarks, he said Moscow respected the African peace proposal on Ukraine and was carefully studying it.

Putin gave the plan a cool reception when a group of African presidents presented it to him last month, responding with a litany of Russian grievances against Ukraine and the West.

Russia has long said it is open to talks but that these must take account of the "new realities" on the ground, where it controls nearly a fifth of Ukraine's territory after 17 months of war and has claimed four Ukrainian regions as its own.

Ukrainian President Volodymyr Zelenskiy has rejected the idea of a ceasefire now that would leave Russia in control of that land and give its forces time to regroup.