The Sri Lankan government has decided to formally withdraw from a cease-fire agreement with Tamil Tiger rebels.

Government officials say the country's Cabinet decided to annul the 2002 Norwegian-brokered truce Wednesday, after a proposal from Sri Lankan Prime Minister Ratnasiri Wickremanayake.

Tamil rebels have not responded to the development.

Under the cease-fire agreement, Sri Lanka must give 14 days written notice to Norway in order to pull out.

Last week, Sri Lanka's defense secretary, the president's brother, Gotabhaya Rajapakse, called for an end to the truce with the rebel group, saying it had been violated so many times it had become a joke.

Both sides have repeatedly ignored the agreement over the past year.

Today's announcement came hours after a roadside bomb targeting an army bus in the capital, Colombo, killed at least four people.

Shortly after the bombing in Colombo, the military retaliated with air strikes inside rebel-held territory in the north. Tamil rebels denied responsibility for the explosion.

The U.S. embassy in Sri Lanka has condemned the attack, and urged the government and rebels to find a peaceful, negotiated solution to the 25-year-long conflict.

Tamil Tiger rebels have fought the government since 1983 to create a separate homeland for ethnic minority Tamils, claiming discrimination from the Sinhalese majority. Some 70,000 people have been killed.

Some information for this report was provided by AP and Reuters.