A series of bomb blasts in the southern Philippines has killed at least six and injured scores of people. There has been a surge in violence in the conflict-ridden region.

The first bomb exploded a few hundred meters from a Roman Catholic church in Jolo, the capital of Sulu province, Tuesday morning. Lieutenant Colonel Edgard Arevalo, a Philippine military spokesman, says the bomb was hidden in a parked motorcycle.

"Some people were able to observe that it seems the motorcycle had wires protruding," he said. "They got suspicious and they called for police assistance. Unfortunately, the device exploded as they were responding to the call."

A few hours later, a bomb exploded in the commercial district of Iligan City. A bomb also destroyed an electricity transmission tower outside the city, leaving a portion of Mindanao island without power.

Tuesday's blasts are the latest in a surge in violence this week in the region. The military has been on high alert since Sunday's explosion outside a church in Cotabato city that killed five people.

Security officials have yet to determine who is behind the attacks. A handful of Muslim rebel and terrorist groups operate in the southern Philippines, including the regional terrorist organization, Jemaah Islamiyah.

Major General Juancho Saban, head of a military task force in Sulu, said they are looking into a possible collaboration between Jemaah Islamiyah and members of the separatist Moro Islamic Liberation Front and the extremist Abu Sayyaf. He says Jemaah Islamiyah militants come to the region and train local rebels in bomb-making.

JI has been blamed for deadly bombings in Southeast Asia, including attacks in Bali, Indonesia in 2002 and 2005.

The Philippine president's office says the recent violent incidents underscore the need to continue engaging with the MILF. But formal peace talks between the government and the insurgents have been stalled for a year.

The Philippine population is predominately Christian, but the southern islands have a large Muslim community. For more than three decades, insurgent groups have fought for a Muslim homeland in the south.