ZAPORIZHZHIA, Ukraine - Authorities in the Ukrainian city of Zaporizhzhia near Europe's largest nuclear plant, under Russian control, said Thursday they are preparing for the "worst" as fears of sabotage mount. Kyiv and Moscow accused each other this week of planning an incident at the plant, which fell to Russian forces at the start of their invasion launched in February last year. Kyiv has said Russia has placed explosives on the plant and President Volodymyr Zelensky has urged the international community to intervene. On Thursday, the Ukrainian military said tensions had "decreased" at the plant thanks to the armed forces and foreign-aided diplomatic efforts. But in Zaporizhzhia, a city with a pre-war population of around 750,000 people just 50 kilometres (30 miles) from the plant, authorities and residents are readying in case of a radiation leak. Memories of the Chernobyl disaster -- that hit Ukraine in 1986 -- still haunt the war-torn country. "It's a major threat," Olena Zhuk, the head of Zaporizhzhia's regional council told AFP, adding: "people are preparing, the government is preparing". At the end of June, city authorities held drills to simulate the mass evacuation of 138,000 people living within 50 kilometres of the plant. That would be "the worst case scenario," Zhuk said. Authorities would initiate various responses depending on the "type" of incident at the plant, she said, adding potential fallout could be "local, very local or not local." She said she believes Russia might stage an incident if Kyiv's forces advanced to the area in their counter-offensive. Ukraine's health ministry has issued a statement to follow evacuation orders "in case of an explosion." It said residents most exposed to the radiation threat could be informed of evacuation points. Kyiv has since early June gone on the advance in several parts of the front, including to the east of the power plant. Moscow has, meanwhile, accused Ukraine of planning "sabotage" acts and strikes on the nuclear power plant.