Ukrainian President Volodymyr Zelensky has urged the international community to "react immediately" to force Russian forces to leave the occupied Zaporizhzhia nuclear plant that was shelled in recent days.

"The entire world must react immediately to chase out the occupiers from Zaporizhzhia. Only the Russians' full withdrawal... would guarantee nuclear safety for all of Europe," he said in his latest video address.

He added: "Only the Russians' full withdrawal... would guarantee nuclear safety for all of Europe" and condemned what he called "Russian nuclear blackmail".

The nuclear plant in southern Ukraine is Europe's largest and has been occupied by Russian troops since March, shortly after Moscow launched its invasion on 24 February.

Russian and Ukraine have traded blame over a recent escalation in fighting around Zaporizhzhia.

The head of the UN nuclear watchdog told the Security Council that the agency must be allowed to inspect the nuclear plant, saying that fighting near the site has sparked a "grave" crisis.

"This is a serious hour, a grave hour and the IAEA (International Atomic Energy Agency) must be allowed to conduct its mission to Zaporizhzhia as soon as possible," Rafael Grossi told an emergency meeting of the Security Council via video feed.

Earlier, the US backed a call for a demilitarised zone around Ukraine's Zaporizhzhia nuclear plant, according to the State Department.

The United Nations Secretary General earlier appealed for an end to all military activities around the plant and warned of "catastrophic consequences" if it is hit.

António Guterres said that he is gravely concerned at the unfolding situation "in and around" the Zaporizhzhia complex.

Mr Guterres urged Ukraine and Russia to give the UN nuclear watchdog, the International Atomic Energy Agency (IAEA), immediate and unfettered access to the site.

Both Moscow and Kyiv said that there were five rocket strikes near a radioactive material storage area today.

Ukraine's nuclear agency, Energoatom, pointed to Russian shelling near one of the plant's six reactors, claiming that it had caused "extensive smoke" and that "several radiation sensors are damaged".

We need your consent to load this rte-player contentWe use rte-player to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage Preferences

The G7 group of most industrialised nations warned yesterday that Russia's continued occupation of the plant "endangers the region" and called for the return of the facility to Ukrainian control.

The tension has brought back memories of the 1986 Chernobyl nuclear disaster in then-Soviet Ukraine, which killed hundreds of people and spread radioactive contamination over much of Europe.

Read more Ukraine war stories

Heavy fighting rages on around the eastern Ukrainian town of Pisky, as Russia pressed its campaign to seize all of the industrialised Donbas region, while to the west Kyiv accused Moscow of using a nuclear plant to shield its artillery.

An official with the Russia-backed Donetsk People's Republic said Pisky, on the frontlines just 10 km northwest of provincial capital Donetsk, was under control of Russian and separatist forces.

"It's hot in Pisky. The town is ours but there remain scattered pockets of resistance in its north and west," the official, Danil Bezsonov, said on Telegram.

Ukrainian officials denied that the heavily fortified town, a key to the defence of Donetsk, had fallen. Neither claim could be independently verified.

The Donbas region, comprised of the Luhansk and Donetsk provinces, became Moscow's main objective after it failed to seize the capital Kyiv at the start of the war in February. Luhansk is now almost completely under Russian control but Donetsk is still holding out.

Oleksiy Arestovych, a Ukrainian presidential adviser, said in an interview posted on YouTube that Russian "movement into Pisky" had been "without success".

Luhansk regional Governor Serhiy Gaidai, interviewed on Ukrainian TV, said Russia had sent increasing numbers of mercenaries into the region, including from the Wagner private security firm.

"We once had peaceful Ukrainian towns. Now we have been thrust into the Middle Ages ... People are now leaving because they are afraid of freezing in the coming winter," he said.