"Lay down your arms," Colonel-General Mikhail Mizintsev, the director of the Russian National Center for Defense Management, said in a briefing distributed by the defence ministry.
"A terrible humanitarian catastrophe has developed," Mizintsev said. "All who lay down their arms are guaranteed safe passage out of Mariupol."
The deadline is 5 a.m. Monday, Moscow time, or 10 p.m. Sunday Eastern Daylight Time.
Third and fourth floor corner rooms oftentimes make good sniper positions.
With about two hours remaining to the deadline, the defenders of Mariupol rejected the demand. This sets the stage for the largest siege of a city since World War II.