"As far as an iron curtain is concerned, essentially it is already descending," Lavrov told reporters.

"We do not prevent the export of Ukrainian grain. The Ukrainian military has mined the approaches to their ports, no one prevents them from clearing those mines and we guarantee the safety of shipping grain out of there," Putin said, speaking alongside visiting Indonesian President Joko "Jokowi" Widodo.

Jokowi, who is the current G20 president, was speaking at a news conference alongside Russian counterpart Vladimir Putin after a bilateral meeting in Moscow.

"With Sweden and Finland, we don't have the problems that we have with Ukraine. They want to join NATO, go ahead," Putin told Russian state television after talks with regional leaders in the central Asian ex-Soviet state of Turkmenistan.

Ukrainian authorities said they were trying to evacuate residents from the frontline eastern city of Lysychansk, the focus of Russia's attacks where about 15,000 people remained under relentless shelling.

It was not immediately clear how Zelensky responded to the offer made by Jokowi during talks in Kyiv or whether the Ukrainian leader had any message he wished to send to Putin.

"Certainly I accept the invitation. Ukraine's participation will depend on the security situation in the country and on the composition of the summit's participants," Zelensky said following their talks in Kyiv, in an apparent reference to Russian President Vladimir Putin's attendance.

Indonesia holds the rotating presidency of the G20 this year and Jakarta has come under Western pressure to exclude Russia's president from the gathering after announcing in April he had been invited. 

President Jokowi and his wife arrived in the Ukrainian capital Kyiv by train, the Indonesian presidential website said.

Jokowi and his entourage have boarded a special train to Kyiv, where the President is to meet Ukrainian President Volodymyr Zelensky to discuss a peaceful solution to end the war.

Indonesia holds the rotating presidency of the G20 this year and Western countries have pressured Jokowi to exclude Russia's president from the summit, after announcing in April he had been invited. 

President Joko "Jokowi" Widodo reiterated Indonesia’s Group of 20 aim of achieving a sustainable energy transition, while also appealing for an end to global food supply chain disruptions caused by the war.

More than 1,000 people were inside when two Russian missiles slammed into the mall in the city of Kremenchuk, southeast of Kyiv, Zelensky wrote on Telegram. At least 16 people were killed and 59 injured, Ukraine's emergency services said. Rescuers trawled through mangled metal and debris for survivors.

In a statement on "resilient democracies" that did not explicitly mention Russia or Ukraine, the G7, India, Indonesia, Senegal, Argentina and South Africa reaffirmed their commitment to the rules-based international order.

"We have received the official invitation... and we have responded positively, saying we are interested in participating," Yuri Ushakov told reporters.

Scholz said that the group of major developed and developing economies will continue to play a "big role" and cooperation was key.

US President Joe Biden and his counterparts from the Group of Seven rich nations, meeting for three days in the Bavarian Alps, promised to tighten the economic screws on Moscow over its February 24 invasion.

Scholz, speaking to German television from the G7 summit he is hosting in the Bavarian Alps, said it was important not to "torpedo" the G20 summit. Ukrainian President Volodymyr Zelenskiy will address the G7 leaders on Monday on a video call.

As the besuited leaders sat down for their first meeting of the three-day G7 summit in the sweltering Bavarian Alps, British Prime Minister Boris Johnson asked if their jackets should come off - or if they should even disrobe further.

Russia's Feb. 24 invasion has killed thousands of people, displaced millions more and led to severe financial sanctions from the West, which Putin says are a reason to build stronger trade ties with other powers such as China, India and Iran.

The Partnership for Global Infrastructure and Investment, unveiled with fanfare by US President Joe Biden and G7 allies from Canada, Germany, Italy, Japan and the European Union, aims to fill a huge gap left as communist China uses its economic clout to stretch diplomatic tentacles into the furthest reaches of the world.

President Joko “Jokowi” Widodo has left for Europe on a peace-building mission, where he is expected to meet with his Ukrainian and Russian counterparts in an effort to broker peace talks between the warring countries, following a visit to Germany to attend the Group of Seven summit.

"Together, the G7 will announce that we will ban the import of Russian gold, a major export that rakes in tens of billions of dollars for Russia," President Joe Biden said on Twitter.

Up to four explosions rang out in central Kyiv in the early hours, in the first such attack on the city in weeks. Two more blasts were heard on the southern outskirts of the city later in the day, a Reuters reporter said.

"We have to stay together," Biden told Scholz at a meeting ahead of the G7 summit in the German Alps.

WHO director-general Tedros Adhanom Ghebreyesus convened a committee of experts on Thursday to advise him whether to sound the UN health agency's strongest alarm over the outbreak.

The summit takes place against a darker backdrop than last year when the British, Canadian, French, German, Italian, Japanese and US leaders met for the first time since before the COVID-19 pandemic and vowed to build back better.

"War has to be stopped and global food supply chains need to be reactivated," Jokowi said before leaving for Germany to attend the G7 summit on Monday.

The Highly Pathogenic Avian Influenza (HPAI) was detected this month in a polar seagull found dead in the archipelago's capital Longyearbyen, the governor's office said in a statement Thursday.

"We face an unprecedented global hunger crisis," Guterres told the meeting in Berlin via video. "The war in Ukraine has compounded problems that have been brewing for years: climate disruption; the COVID-19 pandemic; the deeply unequal recovery."