Both Moscow and Kyiv said there were five rocket strikes near a radioactive material storage area at the plant, Europe's biggest nuclear facility which has been a focus of renewed fighting in recent days.

Ukraine's nuclear agency Energoatom said later there had been fresh Russian shelling near one of the plant's six reactors that had caused "extensive smoke" and "several radiation sensors are damaged".

Vladimir Rogov, a member of the Moscow-installed regional administration, said Ukrainian forces "once again struck" the plant on messaging app Telegram.

The Ukrainian plant is under the control of Russian troops and Ukraine has accused Moscow of basing hundreds of soldiers and storing arms there.

Ukrainian President Volodymyr Zelensky has warned Russia could cause an incident "even more catastrophic than Chernobyl" -- a reference to the nuclear disaster in then Soviet Ukraine in 1986.

United Nations chief Antonio Guterres also said in a statement that continued hostilities around the facility could "lead to disaster".

He urged both sides "to cease immediately" all military activity near the power plant.

The US State Department later on Thursday said the United States supported calls by the UN and others to establish a demilitarised zone around the plant.

"We continue to call on Russia to cease all military operations at or near Ukrainian nuclear facilities and return full control to Ukraine, and support Ukrainian calls for a demilitarized zone around the nuclear power plant," said a State Department spokesperson.

The Security Council is expected to meet at 1900 GMT.

- 'State sponsor of terrorism' -

The Soviet-era plant in southern Ukraine was captured by Russian troops at the beginning of March -- shortly after Moscow launched its invasion and has remained on the frontline since then.

"Russia has turned the nuclear station into a battlefield," Zelensky said, addressing a Ukraine donors conference in Copenhagen by video link.

He called for stronger sanctions against Russia saying it was a "terrorist state" -- on the same day that Latvian MPs adopted a resolution calling Russia a "state sponsor of terrorism".

The statement said Russia's actions in Ukraine constituted "targeted genocide against the Ukrainian people" and said the use of violence against civilians should be considered "terrorism".

Ukrainian Foreign Minister Dmytro Kuleba hailed it as a "timely move" and urged other countries to follow suit, while Russian foreign ministry spokeswoman Maria Zakharova called it "xenophobia".

Latvia has also urged all EU countries to ban tourist visas for Russian citizens and said the measure should be extended to Belarusians because of the Belarusian regime's support for the invasion.

- 'They will advance' -

The fighting meanwhile rumbled on in eastern Ukraine, where Russia-backed separatists have been fighting against Ukrainian forces since 2014.

In the bombed-out town of Soledar, the few residents left are living in underground shelters.

"We hope for the best, but every day it turns out worse and worse," said Svitlana Klymenko, 62, as the relentless shelling continued outside.

Another man living in the shelter, 59-year-old Oleg Makeev said: "You can't cook anything normally here, you can't wash yourself. How am I supposed to feel?".

A soldier, 27-year-old Mykhailo, who had the word "Freedom" tattooed over one eye, said the military were also "sitting in the trenches".

"There is a lot of their artillery, mortars, and we cannot react, we have nothing."

"They will advance further," he said. "We hide more than do anything useful."