Here are the latest developments in the war in Ukraine:

Russia says it has captured the strategic town of Lyman and claims to have surrounded the urban centre of Severodonetsk, as it wages an all-out war for the eastern Donbas -- Ukraine's industrial heartland.

But a Ukrainian official denies the claim that Severodonetsk has been encircled, saying government troops had repelled Russian forces from the outskirts of the key city.

In Severodentsk, where an estimated 15,000 civilians remain, a local official says "constant shelling" has made it increasingly difficult to get in or out.

Evacuation is "very unsafe", with priority given to the wounded and those in need of serious medical assistance, says Oleksandr Stryuk, head of the city's military and civil administration.

The water supply is also increasingly tenuous, as a lack of electricity means the pumps at city wells no longer function, and residents have gone more than two weeks without a cellphone connection, he says.

In his daily address to the nation, Ukrainian President Volodymyr Zelensky says the situation is "very difficult, especially in those areas in the Donbas and Kharkiv regions, where the Russian army is trying to squeeze at least some result for itself".

He says Ukraine is doing "everything" to defend Donbas.

German Chancellor Olaf Scholz and French President Emmanuel Macron ask Russian President Vladimir Putin to hold "direct serious negotiations" with Zelensky.

Ukraine says it is doing 'everything' to defend Donbas Ukraine says it is doing 'everything' to defend Donbas Photo: AFP / Aris Messinis

During an 80-minute conversation with the Russian president, the two EU leaders "insisted on an immediate ceasefire and a withdrawal of Russian troops," the German chancellor's office said.

They also demand Russia free 2,500 Ukrainian fighters taken as prisoners of war after surrendering earlier this month at a sprawling steelworks in the ravaged port city of Mariupol.

With a looming global food crisis exacerbated by the war in Ukraine, Putin says Moscow is "ready" to look for ways to ship grain stuck in Ukrainian ports, but demands the West lift sanctions.

"Russia is ready to help find options for the unhindered export of grain, including the export of Ukrainian grain from the Black Sea ports," Putin tells Macron and Scholz, the Kremlin says.

Putin says the difficulties in supplying grain to world markets were the result of "erroneous economic and financial policies of Western countries".

Putin warns the West that ramping up weapons supplies to Ukraine is "dangerous" and could further destabilise the situation in the pro-Western country.

His remarks come on the heels of US media reports that Washington is preparing to send advanced long-range rocket systems to further help Ukraine.

Pentagon spokesman John Kirby did not confirm the plans to deliver the M270 Multiple Launch Rocket System, a highly mobile system capable of firing up to 300 kilometres (186 miles) that Kyiv has said it badly needs.

But he said Washington was "still committed to helping them succeed on the battlefield".

Russia announces the latest test of its Zircon hypersonic cruise missile, which it says dashed across some 1,000 kilometres (625 miles) and "successfully hit" a target in the Arctic.

As Ukraine faces an increasingly desperate humanitarian situation, an Australian man was reported to have been killed this week while supplying aid.

A death notice appeared in Tasmania's Mercury newspaper identifying the man as Michael Charles O'Neill, 47, with a tribute on Facebook saying he had been "driving the wounded and injured from the front line". An Australian foreign affairs department spokesperson confirmed the death.