At least two police officers were killed and 20 injured in several attacks on Russian security forces in the northern Caucasus region Thursday, Russian news agencies reported according to DPA. Two members of the OMON security police were killed Thursday and 12 injured after shots were fired at a police convoy emerging from a tunnel in the city of Buynaksk in the semi-autonomous republic of Dagestan, Interfax reported, citing Dagestan's Interior Ministry. The security forces were returning from a mission at the time of the attack. Special security forces have begun a search for the perpetrators. Meanwhile, there were three attacks on police officers in Ingushetia, leaving eight with injuries. Unknown assailants started firing a grenade launcher on an Ingushetian Interior Ministry convoy late Wednesday evening near the former capital Nazran, injuring five OMON officers. Underground fighters fired upon ministry troops on Thursday and injured one of them, while two police officers were fired on Wednesday in the same region. Exchanges of fire between units of the Russian police and army and underground fighters are not unusual in the former Soviet republics of Dagestan and Ingushetia that are now part of the Russian Federation, reported DPA.