MOSCOW, July 5 (Xinhuanet) -- A blast at a police station in the capital of Russia's Dagestan republic Tuesday killed two policemen and injured two civilians, the Interfax news agency reported.

    "Preliminary information indicates that the terrorist attack killed two policemen and wounded several others," the report quoted a source of Makhachkala police as saying.

    Law enforcement and security teams in the city rushed to the scene.

    Preliminary investigations suggested that the blast was caused by at least five kilograms of TNT explosives.

    Earlier reports from the scene said the blast killed one policeman and wounded another and three civilians.

    Earlier on Tuesday, an interior ministry official said a large bomb had been found and defused near a theater in the city center.

    It is the second time over the past week that bombs exploded in Makhachkala. The last one took place on July 1, leaving 11 dead and 27 injured.

    According to official figures, at least 30 police officers have been killed this year and at least 40 injured in bombings and shootings in the Dagestan republic in the North Caucasus, most of them in Makhachkala.

    The city has earned the nickname "explosion city" in some Russian media. Enditem