Heavy fighting is again raging around Europe's largest nuclear plant, with Russia and Ukraine accusing each other of shelling the facility.

Russia has accused Ukraine of "taking Europe hostage" by shelling the Zaporizhzhia plant, while Ukraine's President Volodymyr Zelenskyy says Russia is "creating the threat of a nuclear disaster".

Nuclear experts have warned that continued fighting around the site is fraught with danger.

Here's what we know.

1. What is happening at the Zaporizhzhia nuclear plant in Ukraine?

The site was seized by Russian forces in March, but Ukraine is currently staging a counter-attack in the area.

Ukrainian technicians have continued to work at the plant under Russian occupation.

Russia said Ukrainian shelling caused a fire and power surge on Monday, while Ukraine blamed Russia for weekend attacks which it said left three radiation sensors damaged and two workers injured.

The plant appears to still be running, according to Petro Kotin, the head of Ukraine's state nuclear power company Energoatom.

But he has warned that Ukrainian staff at the plant have nowhere to shelter.

Mr Kotin says 500 Russian soldiers and 50 vehicles including tanks, trucks and armoured vehicles are at the site.

2. Where is the Zaporizhzhia plant? How big is it?

The facility, which has six reactors, is located beside the Dnieper river at Enerhodar, south-west of the city of Zaporizhzhia, around 800 kilometres south of Ukraine's capital Kyiv.

The site houses Europe's largest nuclear reactor complex, built during the Soviet era, and its total output is enough to power 4 million homes.

It occupies a key strategic position in southern Ukraine, with both sides fighting for control of the region. 

A reactor building was damaged during fighting around the site in March.

3. How dangerous could it get? Could there be a nuclear accident in Ukraine?

Calling any attack on a nuclear plant "suicidal", United Nations chief Antonio Guterres has demanded UN nuclear inspectors be given access to the site.

Zaporizhzhia's reactors are reinforced with steel and concrete, and designed to withstand an impact from a commercial airliner.

But danger lies in the disruption of the plant's normal safety regime, experts say, with Ukrainian technicians working under stressful and difficult conditions. 

And although nuclear plants can be shut down, their reactors need continual cooling. Any sustained disruption to the electricity supply to cooling pumps could create risks. 

There are also concerns over the site's spent nuclear fuel storage areas, with reports of rocket strikes nearby.

He has described the situation as "completely out of control".

4. What is the risk of a Chernobyl-style nuclear disaster? 

The 1986 Chernobyl meltdown was caused by a specific chain of events which triggered a major explosion and fire, and the release of a plume of radioactive material across Europe. 

Experts say there is little chance of a similar thing happening at Zaporizhzhia.

But the size of the plant, the fighting and the harsh rhetoric from Russia and Ukraine is causing concern.

Nuclear expert Mark Weiman, from Imperial College London, says that despite reports of missile strikes, the spent fuel storage areas are strong and probably don't contain much spent fuel.

5. What is being done to bring things under control at Zaporizhzhia? 

Lots of words, but little action so far.

The UN and IAEA have called for international experts to be allowed in, and Ukraine has called for the site to be recognised as a demilitarised zone.

But there seems little chance of Russia agreeing to this given its strategic value.

Russia has accused the Ukrainians of blocking a visit by IAEA experts.

Russia's RIA Novosti news agency has quoted Moscow's ambassador to the IAEA as saying that Russia is ready to facilitate a visit to the reactor complex.

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