Bombs ripped through a commuter bus and a bridge in the southern Philippines Monday, wounding at least four people and cutting off a vital transportation link, officials said. The bomb exploded at the rear of a commuter bus as it traveled through North Cotabato province's Kabacan town, injuring at least four passengers, said Maj. Randolph Cabangbang, a regional military spokesman. Cabangbang said the blast was under investigation. The Moro rebels are also suspected in the bombing of a bridge early Monday in southern Iligan city that cut off a vital link between several provinces in the south. No one was injured. Rebel spokesman Eid Kabalu denied that his group was behind either of the attacks. Two improvised bombs exploded one minute apart, damaging the 328-feet (100-meter) Agus Bridge, making it impassable, said Army Col. Benito de Leon. Nearby houses and a warehouse were also damaged. De Leon said he suspects rebels angered by the surrender of a guerrilla commander and 20 of his men last week were behind the attack. Malaysian-brokered peace talks between the government and the 11,600-strong rebel group fell apart last August after the Supreme Court blocked the signing of a preliminary accord that would have expanded a Muslim autonomous region in southern Mindanao region. The accord had been challenged by Christian politicians who feared they would lose land, power and clout to minority Muslims in a region torn by a Muslim separatist war for decades. Clashes have sporadically erupted since then.