Police charge 5 in radio host killing MANILA: Muslim militants from the remote southern Philippines may have been behind a bus bomb attack in the nation's financial hub that killed five people, authorities said Wednesday. A mortar bomb triggered by a mobile phone caused Tuesday's explosion that ripped apart a bus travelling along one of Manila's main roads, the city's police chief and President Benigno Aquino's national security adviser said. “A Nokia cellphone is the device they used to trigger the explosion. It acts like a command-detonated explosive,” the security adviser, Cesar Garcia, said on ABS-CBN television. “The fact that the device used was an improvised explosive device similar to the ones used by terrorist organisations in the southern Philippines raises the possibility it was a terrorist attack.” While Garcia said it was too early to say who was behind the blast, he pointed out it was similar to a bus bombing on the same road in Manila that killed four people and injured 36 others on February 14, 2005. “Investigations into the 2005 Valentine's Day bombing showed the suspects rode the bus, carried the (bomb) in a backpack, left the backpack, got off... (and) detonated the bomb with the use of a cellphone,” he said. The Abu Sayyaf, a small group of Islamic militants blamed for the nation's worst terrorist attacks and a string of kidnappings, claimed credit for the 2005 attack, although it has remained silent following Tuesday's explosion. Garcia emphasised that militant groups from the south had long coveted attacks on Manila, which is more than 1,000 kilometres (620 miles) from their strongholds in remote jungles and isolated Muslim-populated towns in the south. “Metro Manila has always been a long-term aspirational target of the organisations operating in the southern Philippines,” Garcia said. Meanwhile, Philippine police filed murder charges Wednesday against a former government official and four other men in the shooting death of a hard-hitting radio commentator who became the country's latest media fatality. Among those charged was a former administrator in southwestern Palawan province who had allegedly owned the gun used by another suspect to kill Jerry Ortega. The broadcaster was fatally shot Monday in a clothing store and the alleged gunman caught moments later with the help of passing firefighters and bystanders. Colleagues believe Ortega, 47, may been have silenced because of his work. The anchor of a morning show on Palawan's DWAR radio station had criticized provincial officials linked to corruption and opposed the operation of mining companies in the resource-rich island province about 220 miles (350 kilometers) southwest of Manila. Besides his local celebrity, Ortega was also well-known in Palawan as a practicing veterinarian who ran a crocodile-breeding farm and headed a local environmental project. Palawan's Puerto Princesa city police chief Rolando Amurao told reporters Tuesday that the suspected assassin, Marlon Recamata Dichaves, had identified other accomplices, including former provincial administrator Romeo Seratubias. Dichaves told police he and an accomplice were promised 150,000 pesos ($3,400) for killing Ortega, Amurao said. Seratubias later surrendered to police and confirmed he was the owner of the gun but said he sold the weapon a few days before Ortega was shot and denied any involvement in the killing, Amurao said.