A team from the U.N. nuclear watchdog was on its way to Ukraine's Zaporizhzhia nuclear plant on Monday, the agency's chief said, as Russia and Ukraine traded accusations of shelling in its vicinity, fueling fears of a radiation disaster.

Captured by Russian troops in March but run by Ukrainian staff, Zaporizhzhia has been a hot spot in a conflict that has settled into a war of attrition fought mainly in Ukraine's east and south six months after Russia launched its invasion.

"We must protect the safety and security of Ukraine's and Europe's biggest nuclear facility," Rafael Grossi, chief of the International Atomic Energy Agency (IAEA), said in a post on Twitter.