Ukraine war: Power back on at huge nuclear plant in Zaporizhzhia

The UN's nuclear watchdog (IAEA) says Ukraine's huge Zaporizhzhia nuclear power plant has begun receiving power from the national grid once again.

Shelling in the area damaged power lines connected to the plant.

All six of its reactors are in a state of cold shutdown, but the plant needs external power to cool its reactors and defend against the risk of a meltdown.

The IAEA says the situation of the plant, which is held by Russian forces, has improved but remains precarious.

The trip followed increasing calls from Ukraine and the international community for a safety inspection following reports of shelling.

Russia and Ukraine both blamed each other for the shelling of the facility in south-east Ukraine.

After the IAEA's first inspection, the agency announced it would maintain a permanent presence in order to monitor the situation.

Members of the team at the site on Saturday learnt that one of the four main external power lines damaged by shelling had been repaired, allowing electricity to be received directly from the national grid, the IAEA tweeted on Saturday.

Further east in Ukraine, the discovery of mass graves in Izyum has led the European Union presidency to call for an international tribunal for war crimes to be carried out.

Hundreds of bodies have been discovered buried in a forest at the edge of the city, which recently came under the control of Ukraine after Russian forces retreated.

Many are said to be civilians, women and children among them.

Ukraine says it believes war crimes have been committed.

"In the 21st Century, such attacks against the civilian population are unthinkable and abhorrent," said Jan Lipavsky, foreign minister of the Czech Republic which holds the EU's rotating presidency.

"We must not overlook it. We stand for the punishment of all war criminals," he wrote in a tweet. "I call for the speedy establishment of a special international tribunal that will prosecute the crime of aggression."

Fighting raged on Saturday in the divided eastern region of Donetsk, which is mostly under the control of Russian-backed separatists.

The separatist mayor of Donetsk city said four people had been killed by Ukrainian government shelling of a central district while the Donetsk region's Ukrainian governor accused Russian forces of shelling a thermal power plant in Mykolaivka, disrupting drinking water supplies in the area.

Ukrainian troops are continuing their counter-offensive in the country's north-east, after successfully recapturing territory from Russia in recent days, the UK's defence ministry says. It adds that Russia has established a defensive line protecting one of its main supply routes from Belgorod, near its border with Ukraine.