KYIV, Ukraine (AP) — Satellite photos of what appeared to be rows upon rows of freshly dug mass graves on the outskirts of Mariupol brought the horrors of the war increasingly into focus as Russia pounded away Friday at Ukrainian holdouts in the city’s steel mill and other targets in a drive to seize the country’s industrial east.

“Every day they drop several bombs on Azovstal,” Petro Andryushchenko, an adviser to Mariupol’s mayor, said of the besieged steelworks. “Fighting, shelling, bombing do not stop.”

Cities elsewhere in the Donbas region also came under Russian fire overnight, and the attacks interfered with efforts to evacuate civilians.

The region, home to coal mines, metal plants, and heavy-equipment factories, is bracing for what could be an epic clash as Russian President Vladimir Putin attempts to salvage a victory from the 8-week-old war widely seen as a blunder and a humanitarian disaster.

On Thursday, Putin claimed victory in the battle for the strategic southern port city of Mariupol, even though an estimated 2,000 Ukrainians remained holed up at the sprawling steelworks, which has been bombarded for weeks. Putin ordered his troops not to storm the stronghold but to seal it off.

At the same time, Maxar Technologies released new satellite images that it said showed more than 200 graves in a town near Mariupol, prompting accusations that the Russians were trying to conceal the slaughter of civilians taking place in the city.

Initial estimates from the Ukrainians said the graves could hold 9,000 bodies, but Andryushenko said there could be more. Ukrainian authorities have said over 20,000 civilians have been killed in the nearly two-month siege of Mariupol.

“The graves have been dug up and corpses are still being dumped there,” the mayor’s aide said.

Putin said Friday that Russia gave Ukrainian forces inside the steel plant the option to surrender, with guarantees to keep them alive, and offered “decent treatment and medical care”, according to an account of a phone call with European Council President Charles Michel provided by the Kremlin.

“But the Kyiv regime does not allow them to take this opportunity,” Putin charged.

Repeated attempts to evacuate civilians from the the city have failed because Russia did not honour ceasefires, Ukrainian officials have said.

Ukrainian Deputy Prime Minister Iryna Vereshchuk said no humanitarian corridors for civilian evacuations would be open in Ukraine on Friday because it was too dangerous. She urged civilians to “be patient” and “hang in there”.

Days into the Russian offensive to take the east, the campaign has yet to become a full-out assault, with military analysts saying Moscow’s forces are still ramping up. But scattered towns in the east have experienced the thud of incoming shells that drive citizens out in panic.

Slovyansk, a city of about 100,000 in eastern Ukraine, came under fire during the night, according to Mayor Vadym Lyakh, who said no injuries were reported. But he urged residents to leave and said a convoy of buses would be organised. In Rubizhne, Russian fire prevented attempts to bring buses in, Luhansk Governor Serhiy Haidai said.