Ukraine: Following the discovery of new mass graves in Ukraine, the President of the European Union on Saturday called for the establishment of an international tribunal for war crimes. "In the twenty-first century, such attacks against civilians are unimaginable and despicable," said Czech Foreign Minister Jan Lipavski, who is currently the rotating president of the European Union. "We must not ignore this. We all support the prosecution of war criminals," he said in a tweet. "I demand that a special international tribunal be established as soon as possible to try the crime of aggression." The appeal comes after Ukrainian authorities discovered some 450 graves outside the formerly Russian-occupied city of Izium, some of which showed signs of torture. In his evening address, Ukrainian President Volodymyr Zelensky said that "new evidence of torture was obtained" from the bodies buried there. He described the discovery of electric torture devices, saying "more than ten torture chambers have already been discovered in various liberated cities and towns of the Kharkiv region." "That's exactly what the Nazis did." That's what Russians do. "And they will be held accountable in the same way - on the battlefield as well as in the courts," he promised. "99 percent of the bodies exhumed today showed signs of violent death," Oleg Sinegubov, the head of the Kharkiv regional administration, said on social media. "Many dead bodies have their hands tied behind their backs, and one person is tied with a rope around his neck," he continued. According to US Secretary of State Antony Blinken, mass graves are more evidence that Russia is committing war crimes in its pro-Western neighbour. French President Emmanuel Macron called the events at Iseume "atrocities". Ukrainian Parliament's Human Rights Commissioner Dmitro Lubinets said that "probably more than 1,000 Ukrainian citizens were tortured and killed in the liberated areas of the Kharkiv region." The United Nations in Geneva has said it hopes to send a team to investigate the deaths. The gruesome discovery came just five months after the Russian army was driven out of Buka near Kyiv, leaving behind hundreds of civilian corpses, many of which contained signs of torture and summary executions. On Thursday, EU commissioner Ursula von der Leyen said Russian President Vladimir Putin should face the International Criminal Court for war crimes committed in Ukraine. After significant losses in his war in Ukraine, US President Joe Biden warned his Russian counterpart Vladimir Putin not to use chemical or strategic nuclear weapons. "Don't. Don't." "No," Biden said in an excerpt from a Friday evening interview with CBS's "60 Minutes." "You will change the face of war in ways that haven't been seen since World War II," Biden said. On the ground, Ukrainian forces have occupied thousands of square kilometers in recent weeks as a result of a counteroffensive in the northeast and are now threatening enemy positions in the south as fighting and bombings continue. "Our forces are pushing them back in their retaliatory strike," said 42-year-old Svitlana Shpuk, an activist in the southern town of Krivi Rih and Zelensky's hometown, which was flooded after Russian missiles destroyed a dam. According to Sinegubov, an 11-year-old girl was killed when missiles fired into the area. Pavlo Kirilenko, the governor of Donestk in eastern Ukraine, which has been partially controlled by Russian-backed separatists since 2014, said on social media Saturday morning that a thermal power plant in Mykolaivka had been "shot by Russian invaders". Ukrainian firefighters were battling the fire, he said, adding that Russian shelling had disrupted water supplies. "The occupiers are deliberately targeting infrastructure in the area to cause as much damage as possible, mainly civilians," he claimed. He had earlier reported that two civilians were killed and 11 others were injured in Russian firing in the past 24 hours. The Kremlin said at its daily briefing in Moscow that it had conducted "high-precision" strikes against Ukrainian positions in the Mykolaiv and Kharkiv regions. Clashes with Russian forces on the eastern side of the Oskil River continued in the northeastern city of Kupiansk, which was captured by Ukrainian forces last week. Some locals took to the streets, where Ukrainian soldiers and volunteers were advancing. A column of smoke rose over the city's east side, where an ammunition depot was on fire. The damaged police station stood deserted in the centre of the small town, the tattered red flag of the Russian army lying on the ground outside. According to a statement issued by the Ukrainian army, "the enemy conducted four missile strikes and 15 air strikes during the day, as well as more than 20 multiple rocket launcher strikes on civilian and military sites in Ukraine." On Saturday, hundreds of Ukrainians attended a farewell ceremony at the national opera house for former ballet dancer and later teacher Oleksandr Shapoval. He was killed in the east of the country at the age of 47. On September 12, near the town of Mayorsk in the Donetsk region, Shapoval was hit by mortar fire. Meanwhile, Ukraine's Zaporizhzhia nuclear power plant has resumed receiving power from the national grid, according to the UN's atomic agency (IAEA), after being cut off from external power, raising the risk of an accident. Due to shelling, the Russian-occupied plant, Europe's largest, had been cut off from the national grid since September. During the two-week outage, the external power supply was running on emergency lines, but these also occasionally failed due to the fighting. The last of the plant's six reactors was shut down last weekend to avoid the need for emergency generators, but the nuclear material still requires cooling. Despite the improved power supply, IAEA chief Rafael Grossi stated that the situation at the plant remains unstable. While the nuclear plant has not been shelled in recent days, fighting has continued in the surrounding area. Shelling around the Zaporozhye nuclear power plant has resumed in Kiev A boy saw his parents being murdered by Russians. Is it going to be a war crime? Vladimir Putin grins as he cautions Ukraine that the conflict could become more serious