The battle for Mariupol reached a decisive stage, with the Ukrainian Marines stationed in the Azovstal industrial area. If the Russians occupy Azovstal, they would have full control of Mariupol, the beacon between Russian-controlled areas to the west and east. The city has already been devastated by weeks of Russian bombing that has killed thousands of civilians. Sign up now for FREE unlimited access to Reuters.com Register Deputy Defense Minister Hanna Malyar said the government was checking unverified information that Russia may have used chemical weapons while besieging Mariupol. “There is a theory that these could be phosphorus munitions,” Malyar said in a televised comment. President Volodymyr Zelenskiy had said Monday night that Russia could resort to chemical weapons as it rallied troops in the eastern Donbass region for a new offensive in Mariupol. He did not say if they were actually used. The United States and Britain have said they are trying to verify the reports. If Russia had used chemical weapons, “all options were on the table” in response, British Defense Secretary James Hippe said in London. The Russian Defense Ministry has not yet responded to a Reuters request for comment. Russian-backed separatist forces in the east have denied using chemical weapons in Mariupol, the Interfax news agency reported. But if it proves to be so, it would mean a dangerous new development in a war that has already left its mark on Russia since Russian President Vladimir Putin sent his troops across the border on February 24. About a quarter of Ukraine’s 44 million people have been forced to flee their homes, cities have been reduced to rubble and thousands have been killed or injured – many of them civilians. Putin has called the move a “special military operation” to demilitarize and “demilitarize” Ukraine, but has sparked condemnation and alarm in the West, which has imposed a wide range of sanctions to strain Russia’s economy. After their troops marched in front of the Ukrainian resistance, the Russians for the time being abandoned their attempt to occupy the capital Kyiv. But they are redoubled their efforts in the east and Ukrainian forces are digging to deal with a new attack. The governor of Luhansk region, Serhiy Gaidai, urged residents to evacuate using five humanitarian corridors agreed for the east. “It is much scarier to stay and burn in your sleep than a Russian shell,” he wrote on social media. “Evacuate, the situation is getting worse every day. Take your basic items and head to the collection point.” A total of nine humanitarian corridors were agreed for Tuesday, including one for private cars from Mariupol, Deputy Prime Minister Iryna Vereshchuk said. In its morning briefing on the conflict, the General Staff of the Ukrainian Armed Forces said that in addition to trying to take control of Mariupol, Russian forces also intended to occupy Popasna, a town about two hours drive west of Luhansk, and They were to launch an attack in the direction of Kurakhove, in the Donetsk region. The Ukrainian military says its troops have repulsed attacks in both Luhansk and Donetsk. President Zelensky overnight called for more weapons from the West to help end the siege of Mariupol and repel the impending Russian attack on the east. “Unfortunately we are not getting what we need to end this war faster … specifically, to lift the blockade of Mariupol,” he said. WAR CRIMES The withdrawal of Russian forces from the outskirts of Kiev has brought to light allegations of war crimes, including the execution and rape of civilians. Moscow denies the allegations as Ukrainian and Western provocations and has also accused Ukrainian forces of sexual violence. Senior UN official Sima Bachus told the UN Security Council on Monday that while all allegations should be investigated independently, “the barbarity shown against Ukrainian civilians has raised all the red flags”. “We hear more and more about rape and sexual violence,” he said. read more “Violence and rape are now being used as weapons of war by Russian invaders in Ukraine,” Kateryna Cherepakha, president of the human rights group La Strada-Ukraine, told the council via video. Russia’s deputy ambassador to the United Nations has denied the allegations and accused Ukraine and its allies of “clearly intending to portray Russian troops as sadistic and rapist.” The Russian Defense Ministry said the Ukrainian government had led the United States to sow false evidence of Russian violence against civilians, despite what it described as “Moscow’s unprecedented measures to rescue civilians.” Putin is scheduled to meet with Belarusian President Alexander Lukashenko on Tuesday to discuss sanctions against Ukraine and Western sanctions, news agencies in Russia and Belarus reported. Belarus is a key area for Russian forces. (This story is corrected on Tuesday in paragraph 1.) Sign up now for FREE unlimited access to Reuters.com Register Report from Reuters’s offices. Written by Simon Cameron-Moore and Angus MacSwan. Editing by Lincoln Feast and Nick Macfie Our role models: The Thomson Reuters Trust Principles.