The military and rebels have been fighting a civil war for more than 20 years, and a truce signed by Prime Minister Ranil Wickremesinghe and the Tamil Tiger rebels' leader Velupillai Prabhakaran in 2002 was thought to be the best chance of permanently ending the conflict. It received widespread international support, especially from the United States, Japan, European Union and India.
Notice of the government's decision to withdraw from the cease-fire will be delivered to peace broker Norway. According to a clause in the truce, either side must give the other 14 days notice when terminating the pact.
"The government had decided to withdraw from the ceasefire," Lakshman Hulugalle, director general of the Media Centre for National Security, told Reuters.
Sri Lanka's Defense Secretary Gotabaya Rajapaka proposed ending the cease-fire Saturday, saying it had been violated so many times that it had lost its viability. The ministers unanimously voted to do so Wednesday.
More than 5,000 people have been killed since early 2006, bringing the death toll since the war began in 1983 to 70,000, Reuters reported.
Tamil Tigers have been waging a separatist war following decades of discrimination by the state controlled by the majority Sinhalese.
The roadside blast on Wednesday killed one soldier and three civilian passers-by, said military spokesman Brig. Udaya Nanayakkara. Colombo National Hospital confirmed the four fatalities, according to the Associated Press.
Nanayakkara said Tamil Tiger rebels were suspected of planting the bomb. The rebels' spokesperson did not return the AP's phone calls.