Separatist rebels were suspected of killing at least two people, wounding eight others and blowing up three natural gas pipelines in India's northeastern Assam state in stepped-up violence ahead of this week's Republican Day holiday. The wave of attacks on Sunday targeted security forces and pipelines belonging to state-owned Assam Gas Co. Ltd. The first killing Sunday occurred when insurgents lobbed a hand grenade at a security checkpoint in the state capital of Gauhati, killing a civilian passer-by and injuring three security officers, state Inspector General of Police Dilip Bora said. In a separate incident, a state police officer was killed when he was ambushed by armed gunmen near the town of Borpathar, 300 kilometers (180 miles) east of Gauhati. Two other grenade attacks occurred Sunday near one of Gauhati's police stations, injuring two police officers and three civilians, Bora said. No one claimed responsibility for the attacks, but officials suspected that ULFA operatives were responsible, Bora said.