Ukrainian forces in the besieged port city of Mariupol have rejected Russia's demands to surrender. Officials say Russian forces have encircled civilians and military personnel.

Russia set a Sunday deadline for Ukrainian forces in the southeastern city to lay down their arms.

But an Azov battalion commander defending the city along with Ukrainian marines told NHK that they will never surrender. He says their fighters in Kyiv are now heading to Mariupol.

Maxim Zhorin said, "Russia has wanted us to surrender since they began their military invasion. But they are so desperate. They have failed to defeat our smaller number of troops."

Ukraine's prime minister said that Mariupol remains in their hands. Denys Shmyhal said, "No, the city still has not fallen. There's still our military forces, our soldiers, so they will fight until the end. And as for now, they still are in Mariupol."

A spokesperson for Russia's Defence Ministry warned that Ukrainians who continue to resist "will be destroyed".

Ukrainian President Volodymyr Zelenskyy has said he will end peace negotiations if there are more casualties in Mariupol.

Further north, Russian forces shelled the country's second largest city on Sunday. The attacks in Kharkiv killed five people and injured 20.

Footage shows emergency workers helping injured people take cover inside a building. The workers and soldiers then carried them out after the shelling stopped.

Kharkiv's Mayor posted a video message on social media, urging residents to evacuate. He said there are no safe places for civilians in the city.

World leaders continue to weigh in on the conflict.

Austria's Chancellor says the Russian President is in what he called "his own war logic." Karl Nehammer met with Vladimir Putin last week.

In an interview with NBC's Meet the Press, he said Putin believes he is winning the war.