Two improvised bombs exploded near a town bridge in southern Philippine city of Iligan early Monday morning, the military said.

Maj Randolph Cabangbang, spokesman of the Armed Forces of the Philippines Eastern Mindanao Command, told reporters that the twin blasts, occurred at around 01:40 a.m. local time (0540 GMT), caused heavy damages to the bridge and nearby houses in Maria Cristina town.

The casualty is not immediately clear.

Hundreds of commuters were stranded as the bridge is located along the highway linking central and western Mindanao. By now, no vehicles could pass the bridge due to the damages.

Troops were sent to pursue suspected bombers who reportedly went into hiding in the mountainous areas.

Iligan, with its share of Christian communities in the Muslims dominating Mindanao region, is a frequent target of bombing attacks planned by the country's radical rebel groups.

Previous bombings in the south were blamed by officials on rouge elements of 11,900-strong Muslim rebels fighting for independence in Mindanao.

Earlier this month, Philippine troops tightened security for possible attacks by militants during the Lenten season.