Vladimir Putin’s forces have launched an “insane” onslaught in the Donbas, Ukrainian officials said on Wednesday.
Heavy fighting was reported in the eastern industrial heartland of Ukraine that Moscow is intent on seizing.
Russian troops have intensified efforts to encircle and capture towns and have continued the relentless bombardment of the city of Sievierodonetsk in the Luhansk area.
Serhiy Haidai, the governor of the Luhansk region, said the area is facing its “most difficult time” in the eight years since separatist fighting erupted.
“The Russians are advancing in all directions at the same time,” he said. “They brought over an insane number of fighters and equipment.
“The invaders are killing our cities, destroying everything around.”
Mr Haidai added that Luhansk is becoming “like Mariupol.”
Workers clearing rubble in the destroyed port city of Mariupol discovered the bodies of 200 people in the basement of an apartment block, it was reported. The bodies were decomposing, said Petro Andryushchenko, an aide to the city’s mayor.
He did not say when the mass grave were discovered, but the number of victims makes it one of the deadliest known attacks in the three months since the war began.
Mariupol was relentlessly hit during in a siege that ended last week when about 2,500 Ukrainian fighters abandoned the sprawling steel plant they had been hiding in.
At least 21,000 people have been killed in the fight for Mariupol, according to Ukrainian authorities.
They have accused Russia of trying to cover up the horrors by bringing in mobile cremation equipment and burying the dead in mass graves.
Ukrainian president Volodymyr Zelensky called the situation unfolding in the Donbas “extremely difficult” as he made a plea for more weapons.
In his nightly address, he said: “I emphasize again and again, the longer this war lasts, the greater will be the price of protecting freedom not only for Ukraine, but also for the whole free world.
“Therefore, the supply of heavy weapons to Ukraine - MLRS, tanks, anti-ship and other weapons - is the best investment in maintaining stability in the world and preventing many severe crises that Russia is still planning or has already provoked.”
They stressed that there had been “no significant” merchant ship movements through Odesa, a huge port on the Black Sea, since the start of the invasion on February 24.
Their warning came just hours after Ukraine’s ambassador to London appeared to reveal that his country and the UK have discussed Royal Navy ships being deployed to create a safe corridor through the Black Sea for cargo ships.
In its latest intelligence briefing, the MoD said: “Ukraine’s overland export mechanisms are highly unlikely to substitute for this shortfall in shipping capacity caused by the Russian blockade.
“As a result, significant supplies of Ukrainian grain remain in storage unable to be exported.”
