MANILA, Philippines -- Hundreds of troops, backed by assault helicopters, launched offensives on two strongholds of a breakaway Muslim guerrilla group in southern Philippines after they attacked at least 14 military camps and outposts, officials said Thursday.

The brazen attacks since Sunday left at least four soldiers dead including one who was beheaded, while at least two rebels were killed in the counteroffensive, according to the government. But a regional army spokesman, Col. Prudencio Asto, said the rebel death toll had reached 15 by Thursday, citing intelligence reports. This could not be independently confirmed.

The rebel group broke off last year from the larger Moro Islamic Liberation Front, which is involved in peace talks with the government. Known as the Bangsamoro Islamic Freedom Movement, it opposes the negotiations, and has vowed to continue fighting for an independent homeland for minority Muslims in the south of the predominantly Roman Catholic nation.