In one of the deadliest clashes in the southern Philippines in recent years, 23 soldiers and at least 20 suspected terrorists have been killed as government troops stormed training camps of the Islamist militants Abu Sayyaf, military officials said Thursday. More than 400 soldiers and police commandos launched pre-dawn attacks Wednesday against jungle camps on Basilan, an island province in the southern Philippines. Abu Sayyaf, which was founded on Basilan in 1991, has been linked by Western and Asian intelligence agencies to Al Qaeda and is on a United States government list of foreign terrorist organizations. Although weakened in recent years, the group continues to have a presence in the south with ambushes of government forces and kidnappings of aid workers and journalists. Maj. Gen. Benjamin Dolorfino, commander of the Western Mindanao Command of the Philippine military, told reporters Thursday that 20 marines and three army soldiers had died in the raids on the camps. He said an initial body count of 20 dead militants was likely to rise. Two senior Abu Sayyaf leaders, Khair Mundus and Furuji Indama, had been the principal targets of the raids, said Lt. Steffani Cacho, an army spokeswoman, although she said it was not immediately clear whether they were among the dead. The raids began at 3 a.m. and lasted until evening, General Dolorfino said. The camps were being used for explosives training, according to an army spokesman, Lt. Col. Romeo Brawner Jr., who added that bomb-making materials and devices had been seized. The fighting Wednesday was the latest in a series of clashes between government forces and insurgents in recent months. In February, several Abu Sayyaf members were killed as soldiers sought to rescue Eugenio Vagni, an Italian Red Cross worker who was abducted with two colleagues in January. After Mr. Vagni was released by his Abu Sayyaf kidnappers last month, the Philippine defense department announced new offensives against the group and sent a surge of fresh troops into Basilan. The message of the government is clear: We will not make compromises with terrorists, Defense Secretary Gilbert Teodoro said at the time. Lets not stop. Lets intensify our counterterror efforts in Basilan so we can conquer the Abu Sayyaf once and for all. United States troops were initially sent to Basilan, beginning in 2002, to help train the Philippine military to counter Abu Sayyaf. Those efforts have substantially weakened the group, officials here in Manila say, but Abu Sayyaf has begun to build alliances with Jemaah Islamiyah, the Southeast Asian terrorist network, to develop its bomb-making expertise. Lately, military officials say, Abu Sayyaf has degenerated into kidnapping, extortion and banditry, using ransom payments to finance its operations.