Vienna, April 2 : Rafael Mariano Grossi, Director-General of the Vienna-based International Atomic Energy Agency (IAEA), said he would head an assistance and support mission to Ukraine's Chernobyl nuclear power plant "as soon as possible" to help ensure the facility's safety. In a tweet, Grossi said that the mission "will be the first in a series of such nuclear safety and security missions to Ukraine", reports Xinhua news agency He also told a press conference in Vienna that the IAEA mission would be in Chernobyl "very, very soon". The IAEA chief has just returned from his recent visits to Ukraine and Russia, during which he held discussions with officials on both sides about ensuring the security of the war-torn nation's nuclear facilities. The UN nuclear watchdog said on Thursday that Russian forces which had been in control of the Chernobyl plant were leaving the facility and had transferred control of the plant to Ukrainian personnel. At Friday's press conference, Grossi said he had not discussed with Russian officials why Russian forces left Chernobyl. Grossi said the IAEA was still unable to confirm reports that Russian forces were contaminated with radiation at the Chernobyl plant. He added that the general radiation level around the plant was "quite normal". "There was a relatively higher level of localized radiation because of the movement of heavy vehicles at the time of the occupation of the plant, and apparently this might have been the case again on the way out," he said. Ukrainian authorities said Russian forces had been in control of the plant since Moscow started its invasion on February 24. The Chernobyl plant, some 110 km north of the Ukrainian capital of Kiev, witnessed the worst nuclear accident in human history on April 26, 1986. /IANS