MOSCOW, Aug. 24 (Xinhua) -- Two officers were killed and two others wounded in an attack on a Russian armored vehicle in Chechnya Saturday, a source in Russia's law enforcement services said Sunday.

    "Two explosive devices were blown up as an armored personnel carrier was driving along a road not far from the village of Agishty in Shali district. The bombing was accompanied by fire from small arms," the source was quoted by the Interfax news agency as saying.

    Two deputy commanders of an armed forces unit, a lieutenant colonel and a major, were killed, and two other officers were seriously wounded and hospitalized, the source said.

    Another source in the criminal investigation service said the squad, which was part of the Interior Ministry forces, had returned fire.

    The authorities have opened an investigation into the incident and measures were being taken to identify and arrest the attackers, the source said.

    Kremlin launched two military campaigns against Chechen separatist forces in the 1990s and the early 2000s. Although the operation has almost been completed, frequent attacks by militants still occur in the North Caucasus republic.