Two explosions and a shooting killed at least nine people Monday and wounded 17 in troubled Sri Lanka, where an unraveling cease-fire between the government and Tamil rebels is threatening to plunge the country into all-out civil war.

A bomb at an army checkpoint in the northeast killed four police officers, two soldiers and a civilian, the army said. Fourteen others were wounded.

The bomb was hidden in a motorized-rickshaw that blew up when security forces went to check it, army spokesman Brig. Prasad Samarasinghe said. Nine of the injured were hospitalized in serious condition.

CountryWatch: Sri Lanka

No one claimed responsibility for the explosion, which occurred at the entry to the port city of Trincomalee, 135 miles northeast of Colombo, the army said in a statement.

Samarasinghe blamed the blast on separatist Tamil Tiger rebels.

Government forces control the port of Trincomalee, but pockets of surrounding countryside are held by the rebels who have been fighting for more than two decades to turn parts of the north and east into a separate state for the country's ethnic Tamils.

Also Monday, a Claymore mine suspected to have been triggered by rebels in the northern Jaffna Peninsula killed one soldier and wounded another, the army spokesman said. The two were on foot patrol in Nelliady, a small town nearly 200 miles north of Colombo.

Suspected rebels also fired at the soldiers in Vavuniya early Monday. The army returned fire, killing an attacker wearing a Sri Lankan army uniform, an army statement said.

Another Claymore mine was triggered while commandos were checking a road for mines in the eastern district of Batticaloa before military vehicles were scheduled to pass, injuring both of them, Samarasinghe said.

The mines are a weapon favored by rebels, who have been fighting since 1983 for a separate homeland for minority ethnic Tamils. More than 65,000 people have died in the conflict.

A 2002 cease-fire halted the fighting. But subsequent peace talks broke down, and a recent escalation of violence has killed more than 700 people since April, threatening a return to full-scale war.