President Volodymyr Zelensky secured more arms, munitions and "unwavering" diplomatic support from G7 allies in Hiroshima Sunday, as Russia claimed victory in the battle for a devastated eastern city.

Meeting leaders from a bloc of rich democracies, Zelensky won a commitment from US President Joe Biden to provide yet more "ammunition, artillery, armoured vehicles" on top of access to F-16 jets.

Top Zelensky aide Andriy Yermak said the US package included additional ammunition for HIMAR rocket launchers, artillery shells, anti-tank guided missiles and thermal imaging systems worth $375 million.

Zelensky's surprise trip to Japan has been a major diplomatic coup, putting his country and Russia's 15-month-long invasion firmly at the top of the agenda.

But success in the negotiating rooms contrasted sharply with difficulties on the ground, as he reflected on the months-long battle for Bakhmut and new Russian claims to have taken control of the eastern city.

Asked about the fate of the former salt-mining town of 70,000 people, Zelensky was notably downbeat, saying "you have to understand there is nothing" there. 

"For today, Bakhmut is only in our hearts," he said.

Ukrainian forces have tried for months to keep a toehold on the town, forcing Moscow to commit significant numbers of troops there in the process.

On Saturday, Russian President Vladimir Putin congratulated mercenaries from the Wagner organisation and regular units for the operation to "liberate" the town.

Zelensky's invitation to visit Hiroshima, a city synonymous with the horrors of nuclear war, was a "deeply meaningful" symbol of support, according to host Fumio Kishida, Japan's prime minister.

"By inviting President Zelensky to Japan, we demonstrated the unwavering solidarity of G7 with Ukraine," he said. 

As well as securing backing from allies, the visit afforded Zelensky a rare opportunity to win over a handful of nations who have pointedly offered little or no condemnation of Russia's invasion. 

Leaders from India, Brazil, Vietnam and Indonesia were among those invited to attend the summit as non-members.

- 'I understand your pain' -

Brazil's President Luiz Inacio Lula da Silva has accused the West of "encouraging the war" and is yet to confirm he will even meet his Ukrainian counterpart.

The reception was warmer however from India's Prime Minister Narendra Modi, who told Zelensky: "I understand your pain and the pain of Ukrainian citizens very well."

"I can assure you that to resolve this India and, me personally, will do whatever we can do."

Zelensky offered an upbeat assessment of the encounter, saying he believed India "will participate in the restoration of the rules-based international order that all free nations clearly need."

Zelensky is also looking for support for a 10-point peace plan, centred on the demand that Russia retreat from Ukrainian territory.

German Chancellor Olaf Scholz said the message from Ukraine and its allies was clear: "Russia must withdraw troops".

Any peace plan, he said, "can't simply be linked to a freeze of the conflict".

"Russia should not bet that if it holds out long enough, it will end up weakening support for Ukraine."

Zelensky had previously been scheduled to attend the G7 summit remotely but arrived on the back of a major breakthrough in his battle to wrest advanced weaponry from the West.

The White House dropped its longstanding reluctance to allow allies to supply Kyiv with F-16 fighter jets, opening the way for Ukraine to receive its most sophisticated material yet.

Washington insisted the aircraft were part of a US strategy to support Ukraine "in a way that avoids World War III", and deflected criticism that their decision was too long coming.

Zelensky acknowledged the jets would not help the war effort immediately but hailed the decision as "a great result".

Mick Ryan, a strategist and retired Australian major general, called the decision "very significant".

"F-16s have the sensors and weapon systems that are either equal to, or overmatch, Russian fighters," he told AFP.

While Ukraine has dominated the summit, the leaders have also taken aim at China, with a thinly veiled statement denouncing efforts to "weaponise" trade and supply chains, and warning they would "fail and face consequences".

The grouping also warned China against its "militarisation" in the South China Sea and urged Beijing to press Russia to end its invasion of Ukraine.

It insisted however that it still seeks "constructive and stable relations" with China.

China hit back late Saturday, expressing its "strong dissatisfaction" with the G7's final communique, and Russia too lashed out at the group's efforts to "contain" Beijing and Moscow.

bur-sah/arb/pbt