This was reported on Facebook page of Interior Minister Arsen Avakov, Censor.NET reports.
"The area of operation in the center of Mariupol is cordoned off. The operation involves a unit of the National Guard of Ukraine, Ministry of Internal Affairs Special Forces "Azov" and "Dnipro-1". The checkpoints around Mariupol are strengthened by our armed forces. The operation started at 4.50 a.m and is proceeding successfully according to the plan. All the key strongholds of the terrorists have been brought under control. The BRDM was destroyed as well as sniping spots. The terrorist losses are high. There are no casualties on our side - two soldiers were wounded. The operation continues," Avakov said.
"It is a pity that today Mariupol was awaken by shots, but the city of steelworkers must live and work not to the tune of bandits!" the Minister wrote.