Kyiv, Ukraine: Ukraine said Thursday Russia was "trying to destroy" its remaining soldiers holed up in Mariupol's Azovstal steel plant, with Kyiv's last defenders in the battered city saying Moscow forces have broken into the giant factory. "Russian occupiers are focusing on blocking and trying to destroy Ukrainian units in the Azovstal area," Kyiv's army said in a statement. "With the support of aircraft, Russia resumed the offensive in order to take control of the plant." The statement came as a Russian-announced ceasefire was due to begin at the besieged plant, where hundreds of Ukrainian soldiers and some civilians have been trapped for weeks. A commander of the Azov battalion, leading the defense of Mariupol, said late on Wednesday that Russian soldiers have entered the plant and that there were "ongoing, bloody battles." "For two days, the enemy has burst into the enclosure of the steelworks," Azov commander Denys Prokopenko said in a video on Telegram. "The situation is extremely difficult but despite this we continue to execute the order to hold the defence." He said the Ukrainian units were "resisting" while being outnumbered by the Russians. Ukrainian President Volodymyr Zelensky on Wednesday asked UN chief Antonio Guterres to help "save" his units in Azovstal, calling for "the removal of all the wounded". The Ukrainian leader said in a separate video address later that there were still civilians -- "women and children" stuck at Azovstal and that Kyiv was "negotiating" to rescue them. "It takes time to simply lift people out of these underground shelters," he said. "In current conditions, we cannot use special equipment to clear the debris. Everything is done manually." Mariupol Mayor Vadym Boichenko on Thursday called for the continuation of UN- and Red Cross-led evacuations from the southern port city. "Now we are fighting for the salvation of every person, every Mariupol resident," he said on Telegram. A further 344 Ukrainians were evacuated from Mariupol and its surroundings late on Wednesday. Fighting also raged in other parts of eastern Ukraine, with the governor of the Donbas region Pavlo Kyrylenko saying at least 25 civilians were wounded in an overnight Russian strike on the city of Kramatorsk.