Ukrainian troops in Mariupol have refused to surrender after Russia issued a warning that those who do not put down their weapons would be "destroyed". 

Russia has claimed that an estimated 2500 Ukrainian fighters holding out at a hulking steel plant were the last pocket of resistance in the port city. 

The deadline for surrender has passed but troops did not submit to the demands of the invading force. 

“All those who will continue resistance will be destroyed,” Maj Gen Igor Konashenkov, the Russian defence ministry’s spokesman, said.

He said intercepted communications indicated there were about 400 foreign mercenaries with the Ukrainian troops at the Azovstal steel mill, a claim that could not be independently verified.

Seizing Mariupol would free Russian forces to weaken and encircle Ukrainian forces in eastern Ukraine. 

The ongoing siege and relentless bombardment of the city has come at a terrible cost, with officials estimating Russians had killed at least 21,000 people.

Just 120,000 people remain in the city, out of a pre-war population of 450,000.

Russia has dedicated attentions on the region and is deploying personnel and equipment withdrawn from the north after a botched attempt to take Kyiv. 

Ukrainian deputy defence minister Hanna Malyar described Mariupol as a “shield defending Ukraine” as Russian troops prepare for a full-scale offensive in Donbas, the country’s eastern industrial heartland where Moscow-backed separatists already control some territory.

In a reminder that no part of Ukraine was immune until the war ends, Russian forces carried out new missile strikes on Sunday near Kyiv and elsewhere in an apparent effort to weaken Ukraine’s military capacity before the anticipated assault in the east.

After the humiliating loss of the flagship of its Black Sea Fleet, Russia’s military command vowed Friday to step up missile strikes on the capital.

The Russian military said Sunday that it had attacked an ammunition plant near Kyiv overnight with precision-guided missiles, the third such strike in as many days.

Russia renewed attacks on Kyiv after accusing Ukrainian forces of airstrikes on Russian territory that wounded seven people and damaged about 100 residential buildings in Bryansk, a region bordering Ukraine. Ukrainian officials have not confirmed hitting targets in Russia.

Kyiv mayor Vitali Klitschko said a strike on Saturday on what Russia’s defence ministry identified as an armoured vehicle plant killed one person and wounded several. He advised residents who fled the city earlier in the war not to return.

The Russian military also claimed Sunday to have destroyed Ukrainian air defence radars in the east, near Sievierodonetsk, as well as several ammunition depots elsewhere.

Explosions were reported overnight in Kramatorsk, an eastern city where rockets killed at least 57 people at a train station crowded with civilians trying to evacuate before the expected Russian offensive.