Russian forces have "completely liberated" the Azovstal steel plant in Mariupol, the Russian Defense Ministry said Friday.

"The underground facilities of the enterprise, in which the militants were hiding, are in complete control of the Russian armed forces," the ministry said in a statement.

"The last group of 531 militants surrendered today," it said, adding that "a total of 2,439 Azov Nazis and Ukrainian soldiers had laid down their arms since May 16."

According to the statement, Russian Defense Minister Sergei Shoigu has reported to Russian President Vladimir Putin on the completion of the operation.