Russian troops struck the Pivdennoukrainsk nuclear power plant in Ukraines southern Mykolaiv region early on Monday but its reactors have not been damaged and are working normally, Ukraines state nuclear company Energoatom said. A blast took place 300 meters (yards) away from the reactors and damaged power plant buildings shortly after midnight, Energoatom said in a statement. The attack has also damaged a nearby hydroelectric power plant and transmission lines. "Currently, all three power units of the PNPP (Pivdennoukrainsk Nuclear Power Plant) are operating normally. Fortunately, there were no casualties among the station staff," Energoatom said. It published two photographs showing a crater it said was caused by the blast. In one of the pictures a man stood in the crater to give a sense of its size. Commenting on the strike on the Telegram messaging app, Ukraines President Volodymyr Zelenskiy said: "The invaders wanted to shoot again, but they forgot what a nuclear power plant is. Russia endangers the whole world. We have to stop it before its too late." There was no immediate Russian reaction to Ukraines accusations. The Mykolaiv region has been under constant rocket attack by Russian forces in recent weeks. Another Ukrainian nuclear power plant at Zaporizhzhia - which is Europes largest and lies about 250 km (155 miles) east of the Mykolaiv site - was shut down earlier this month due to Russian shelling, prompting concerns about a possible nuclear disaster. Russia and Ukraine have blamed each other for shelling at the Zaporizhzhia plant, which is held by Russian forces but operated by Ukrainian staff. The shelling has damaged buildings and disrupted power lines. The UN nuclear watchdog said this weekend one of the four main power lines at the Russian-held Zaporizhzhia nuclear facility had been repaired and was once again supplying the plant with electricity from the Ukrainian grid.