Mariupol came under further heavy bombardment overnight, according to a Ukrainian officer inside the city.
“Bombs are falling every 10 minutes; Russian navy warships are shelling. Yesterday the soldiers defused four tanks, [as well as] armored vehicles and troops. We still need ammunition, anti-tank weapons and air defense," Captain Svyatoslav Palamar of the National Guard Azov Regiment in Mariupol told CNN.
Palamar said he and his fellow fighters would not surrender in Mariupol.
Some background: The Russian-issued deadline for Mariupol authorities to surrender the city passed at 5 a.m. Moscow (10 p.m. ET Sunday), with Ukrainians rejecting the ultimatum.
The port city of Mariupol, which before the war was home to around 450,000 people, has been under near constant attack from Russian forces since early March with satellite images showing significant destruction to residential areas.
While the Russian ultimatum appeared to offer those who chose to surrender safe passage out of the city, it made no such guarantees for those remaining.
Russia has repeatedly been accused of targeting civilians, with trapped residents describing the onslaught as "hell."
The Russian attacks have led to a total collapse in basic services, with residents unable to access gas, electricity or water. Bodies are being left in the street because there is either no one left to collect them, or it is simply too dangerous to try.
An official in the city said people are scared to leave their underground shelters even to get hold of essentials, meaning they were trying to drink less water and eat less food, only emerging to prepare hot meals.
Taken against their will: On Sunday, the Mariupol City Council said residents are being taken to Russia against their will by Russian forces. Captured Mariupol residents were taken to camps where Russian forces checked their phones and documents, then redirected some of the residents to remote cities in Russia, the council said. Russia denied the accusations Saturday.
Why Russia wants to control Mariupol: The city is a strategic port that lies on a stretch of coast connecting the eastern Ukrainian region of Donbas with the Crimean peninsula. Russian-backed separatists have formed breakaway statelets in parts of the Donbas and Crimea has been under Russian control since 2014. Russian forces appear to be trying to take full control of the area to create a land corridor between the two regions, squeezing Mariupol with brutal military force.