Russian forces have shelled the entire front line of Donetsk region in eastern Ukraine, Ukrainian officials say, part of what appears to be the Kremlin’s scaled-back ambition to secure only the bulk of lands it has claimed.

The fiercest fighting was near the towns of Bakhmut and Avdiivka, the region’s governor Pavlo Kyrylenko said in a TV interview on Thursday.

Artillery slammed into the town of Toretsk southwest of Bakhmut, killing one civilian and damaging 12 buildings, Kyrylenko said.

He said “the entire front line is being shelled” and Russian troops were also trying to advance near Lyman, which was recaptured by Ukrainian forces in November, one of a number of setbacks suffered by Russia since invading its neighbour in February.

In Bakhmut and other parts of the Donetsk region that neighbours Luhansk province, Ukrainian forces countered with barrages from rocket launchers, Reuters witnessed.

Ukraine’s military command said Russian artillery attacked civilian infrastructure in the towns of Kupiansk and Zolochiv in the northeastern region of Kharkiv, and Ochakiv in the Mykolaiv region.

Ukrainian anti-aircraft units downed several of the missiles trained on Kharkiv region on Thursday evening, governor Oleh Synehubov said on the Telegram messaging app.

Reuters was not able to verify battlefield reports.

In a reminder that, despite the hostilities, Russia maintains lines of communication with the West, Washington said Moscow had freed US basketball player Brittney Griner in return for the release of Russian arms dealer Viktor Bout.

The White House said the prisoner swap would not change its commitment to the people of Ukraine.

The US House of Representatives passed a defence bill on Thursday that provides Ukraine at least $US800 million ($1.2 billion) in additional security assistance next year.

Separately, a US citizen ordered deported by a Russian court over a domestic dispute left Russia late on Thursday.

In Rome, Pope Francis broke down and cried as he mentioned the suffering of Ukrainians during a traditional prayer.

“Immaculate Virgin, today I would have wanted to bring you the thanks of the Ukrainian people (for peace),” he said before being overwhelmed by emotion and having to stop.

Pope Francis, who was later able to continue speaking, has mentioned Ukraine in nearly all his public appearances since the invasion and has grown increasingly critical of Russia.

President Vladimir Putin has given conflicting statements on the goals of the war but is now clear the aims include some expansion of Russia’s borders, in contrast with comments made at the start of the “special military operation”, when he said Moscow’s plans did not include the occupation of Ukrainian land.

The Kremlin said on Thursday it was still set on securing at least the bulk of the territories in east and south Ukraine that Moscow has declared part of Russia, but appeared to give up on seizing other territory in the west and northeast that Ukraine has recaptured.

Moscow proclaimed in October that it had annexed four provinces shortly after holding so-called referendums that were rejected as bogus and illegal by Ukraine, the West and most countries at the United Nations.

While Moscow made clear it wanted to take full control of Donetsk and Luhansk – two largely Russian-speaking regions collectively known as the Donbas – it left unclear how much of Zaporizhzhia and Kherson it was annexing.

Ukrainian President Volodymyr Zelensky says his troops will eventually drive Russia from all the captured territory, including the Crimea peninsula annexed by Russia in 2014 that sits between the Black Sea and the Sea of Azov.

President Zelensky in his Thursday night video address paid tribute to four policemen killed by landmines in Kherson province.

“This is perhaps even fiercer and more devious than missile terror,” said President Zelensky, whose country has faced barrages of Russian missile and drone strikes.

“For there is no system against mines that could destroy at least part of the threat as our anti-aircraft systems do.”

On Thursday, Russian naval forces shot down a Ukrainian drone over the Black Sea, according to the Russian-installed governor of Sevastopol, an important port and the largest city in Crimea.

– AAP