Vienna, March 9 : The Head of the UN's nuclear watchdog, the IAEA, has appealed the Russian Armed forces, who are effectively in control of the Chernobyl nuclear site in northern Ukraine, to allow some of the staff there to have a break. In a statement, the IAEA Chief Rafael Grossi said the Ukrainian authorities had told him the same group of about 210 workers had been on duty constantly for the past two weeks, the BBC reported. Grossi added that he was deeply concerned about the stressful situation facing the personnel. The employees, he said, must be able to rest and work in regular shifts, stressing that this was crucial for overall nuclear safety. Russian soldiers entered the site of the world's worst nuclear disaster in 1986 on February 24, just hours after Moscow began a full-scale invasion of Ukraine. Grossi also indicated that remote transmission of data from security monitoring systems at the power plant to the IAEA had been lost. /IANS