The commander in chief of Ukraine's armed forces has warned Russian activity is increasing around the key frontline town of Pokrovsk, saying "the situation is difficult".

General Oleksandr Syrskyi admitted Russian infantry was massing in the area and said he had visited the frontline himself for talks with key commanders.

But he said reports that Ukrainian troops had been "blockaded" there by Russian forces was "untrue" propaganda.

There have been growing reports of Russian advances around the strategic town in the Donetsk region in the east of Ukraine. It forms a key transport and supply hub and its capture could unlock Russian efforts to seize the rest of the region.

In a statement on Telegram, General Syrskyi said: "In Pokrovsk, enemy infantry, avoiding combat, is amassing in the urban area and changing locations, so the primary objective is to identify and destroy them."

He added: "The situation is difficult, but Russian propaganda claims about the alleged 'blockade' of the Ukrainian Defence Forces in Pokrovsk, as well as in Kupiansk, are untrue."

He said commanders were having to maintain "a reasonable balance between goals and capabilities."

"The main priority is preserving the lives of our soldiers," he added.

Russian forces have been trying to seize Pokrovsk for more than a year. Taking it would give them a path towards taking the two biggest cities still controlled by Ukraine in the region - Kramatorsk and Sloviansk.

Moscow launched its full-scale invasion of Ukraine in February 2022.

Russia's chief of general staff, Gen Valery Gerasimov, claimed earlier this week Ukrainian troops in Pokrovsk had been surrounded.

Ukrainian President Volodymyr Zelensky said Pokrovsk was "the main target" for Russia whose forces there, he said, outnumbered Ukrainians by eight to one.

He told reporters Russia wanted to take the town to convince the United States that Ukraine was on the run.

"They do not have a result they can 'sell' to the Americans. We understand why they need Pokrovsk. They need it only to claim that Ukraine withdraws from the east and gives everything else they want," Zelensky said.

In its latest assessment, the defence intelligence firm, Sybelline, said the battle for Pokrovsk "has entered a highly dynamic and intense phase, as the Russian forces intensify their efforts to infiltrate the city and encircle Ukrainian defenders".

Deepstate, a Ukrainian monitoring group, said Russian forces were "gradually engulfing" Pokrovsk "with [their] sheer number of personnel".

It said Russian troops were infiltrating deeper into the town and disrupting Ukrainian supply routes.

"The situation in Pokrovsk is on the brink of crisis and continues to deteriorate, to the point where it may be too late to fix everything," the group concluded.