KRAMATORSK, May 19. /ITAR-TASS/. Ukrainian law enforcers have opened fire from mortars on the city of Kramatorsk in eastern Ukraine’s Donetsk Region, one of the mortar shells exploded near an area with country houses, a police spokesman told ITAR-TASS on Monday.

Two other shells exploded outside residential areas. The city's self-defense headquarters said it could be registration of guns.

The police also said three military trucks were spotted 15 kilometers from the center of Kramatorsk between the villages of Belokuzminovka and Semyonovka. The trucks were carrying some 50 people in black uniforms without insignia.

There are problems with cellular communications in the city.

Massive protests against the new Ukrainian authorities, who were propelled to power in Kiev amid riots during a coup in the country in February, erupted in Ukraine’s Russian-speaking southeastern territories after the secession of the Crimean Peninsula, which declared independence on March 11 and joined Russia on March 18 following a referendum.

Kiev has been conducting a punitive operation against pro-federalization activists in southeastern regions of Ukraine.