Philippine President Gloria Macapagal Arroyo was set to sign a landmark anti-terrorism law Tuesday to better fight al-Qaida-linked militants despite objections from left-wing groups it may be used against government critics. The Human Security Act will add legal muscle to a US-backed counterterrorism campaign targeting the Abu Sayyaf group and their allies from Indonesian-based Jemaah Islamiyah in the southern Philippines. The US has long prodded the Philippines to enact legislation to bolster the anti-terror campaign. The Abu Sayyaf has been blamed for deadly bomb attacks, beheadings and kidnappings. Jemaah Islamiyah militants have taken refuge in the southern region of Mindanao, running bomb-making and training camps and plotting attacks with Filipino separatist insurgents.