KYIV, Aug 29 (Reuters) - A team from the U.N. nuclear watchdog headed on Monday to Ukraine's Zaporizhzhia nuclear plant, the agency's chief said, as Russia and Ukraine traded accusations of shelling in its vicinity, fuelling fears of a radiation disaster.

Captured by Russian troops in March but run by Ukrainian staff, Zaporizhzhia has been a hotspot 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, director-general of the International Atomic Energy Agency (IAEA), said in a post on Twitter.

An IAEA team he was leading will reach the plant on the Dnipro river near front lines in southern Ukraine later this week, Grossi said, without specifying the day of their expected arrival.

The IAEA tweeted separately that the mission would assess physical damage, evaluate the conditions in which staff are working at the plant and "determine functionality of safety & security systems". It would also "perform urgent safeguards activities", a reference to keeping track of nuclear material.

The United Nations and Ukraine have called for a withdrawal of military equipment and personnel from the nuclear complex, Europe's largest, to ensure it is not a target.

The two sides have for days exchanged accusations of courting disaster with their attacks.

With fears mounting of a nuclear accident in a country still haunted by the 1986 Chornobyl disaster, Zaporizhzhia authorities are handing out iodine tablets and teaching residents how to use them in case of a radiation leak.