ZAPORIZHZHIA, Aug 31 (Reuters) - United Nations inspectors arrived on Wednesday (Aug 31) in the southern Ukrainian city of Zaporizhzhia on a mission to prevent a nuclear accident at a Russian-occupied power plant where nearby shelling has prompted global fears of disaster.

The International Atomic Energy Agency (IAEA) team reached the city 55km away from the plant, where they were likely to spend the night before arriving at the facility on Thursday.

Although Russian-installed officials suggested the visit might last only one day, the IAEA hopes for longer.

"If we are able to establish a permanent presence, or a continued presence, then it’s going to be prolonged. But this first segment is going to take a few days," its chief, Rafael Grossi, told reporters in Zaporizhzhia.

"It's a mission that seeks to prevent a nuclear accident," he said.

Russia captured the nuclear plant, Europe's largest, in early March and its military force has been there ever since, as has most of the Ukrainian workforce who have toiled to continue running the facility, which had supplied 20 per cent of Ukraine's electricity.

Fighting was reported near the power station and further afield on Wednesday, with Kyiv and Moscow both claiming battlefield successes amid a Ukrainian counter-offensive to recapture southern territory.

Ukraine repelled Russian attempts to attack in the direction of Bakhmut and Avdiivka, two towns located north of the Russian-occupied city of Donetsk, its armed forces' general staff said on Wednesday. Pro-Moscow troops have focused on Bakhmut in their push to extend control over the Donbas region, it said.

Reuters could not independently verify such reports.

Away from Ukraine, Russia halted gas supplies via Europe's key supply route on Wednesday, intensifying an economic battle between Moscow and Brussels that could lead to recession and energy rationing in some of the continent's richest countries.

Neighbour Estonia announced plans to stop most Russians from entering the country within weeks, if possible acting in concert with its regional partners, after the EU was too divided to agree on a blanket ban.

Russia says it is waging a "special military operation" to rid Ukraine of nationalists and protect Russian-speaking communities.

Kyiv and the West describe Russia's actions as an unprovoked war of aggression that has caused millions to flee and turned cities into rubble.