WRAPUP 11-UN inspectors reach Ukraine nuclear plant after shelling causes delay

(Adds some IAEA members seen leaving, return to school)

* Team was delayed several hours by shelling near plant

* Each side accuses other of trying to sabotage IAEA mission

* Shelling reported at Enerhodar, site of plant, overnight

* Ukraine claims successes in counter-offensive

By Tom Balmforth

ZAPORIZHZHIA, Ukraine, Sept 1 (Reuters) - A team of U.N. experts arrived at Europe's biggest atomic power plant after crossing the frontline into Russian-held territory in southern Ukraine on Thursday, to assess the risk of what both sides say could be a devastating radiation disaster.

After being delayed several hours by shelling near the site, the team reached the Zaporizhzhia nuclear power plant in a large convoy with a heavy presence of Russian soldiers nearby.

A Reuters reporting crew operating in Russian-held territory was at the site. Some members of the inspection team left after spending several hours there. Ukraine's nuclear power operator Energoatom said five team members would stay on for two more days.

Russia and Ukraine have accused each other of trying to sabotage the IAEA mission to the plant, which sits on the south bank of a huge reservoir on the Dnipro River that divides Russian and Ukrainian forces in central southern Ukraine. Since the early days of the conflict, the plant has been controlled by Russian troops but operated by Ukrainian staff.

Conditions at the plant have been unravelling for weeks, with Moscow and Kyiv regularly trading blame for shelling in the vicinity, fuelling fears of a Chornobyl-style radiation disaster.

Kyiv also accuses Moscow of using the Russian-controlled plant as a shield for its weapons, which Russia denies, and of planning to switch it from Ukraine's power grid to Russia's, effectively stealing its output.

Russia's Foreign Minister Sergei Lavrov said Moscow was doing everything to ensure that the plant could operate safely, and for the IAEA inspectors to be able to complete their tasks.

"In the event of further attempts by Kyiv to disrupt their work with shelling or sabotage, the entire responsibility for the consequences will fall entirely on the Zelenskiy regime and its handlers and their 'support group' in the West," the Russian foreign ministry said in a statement, referring to Ukraine's President Volodymyr Zelenskiy.

Earlier, Ukraine's state nuclear company Energoatom said Russian shelling had forced the shutdown of one of the two reactors still operating at the site, while Moscow said it had thwarted a Ukrainian attempt to seize the plant.