A bomb killed three security volunteers in Thailand's south while militants shot dead three Muslim civilians as the region entered the holy month of Ramadan, police said Saturday. Suspected insurgents detonated the device as a group of officials heading to investigate an earlier blast in troubled Yala province on Saturday tried to move a felled tree blocking a road, they said. Three civilian security volunteers were killed instantly by the explosion and four were wounded, two of them volunteers and two interior ministry officials. The earlier bomb wounded two soldiers. Thailand's interior ministry trains, pays and arms civilian security volunteers as part of efforts to curb a five-year insurgency in the Muslim-majority south near the Malaysian border.