Wednesday's attack came more than 10 years after the Moro Islamic Liberation Front (MILF) signed a peace agreement with Manila, ending a decades-old armed campaign initially for a separate state and later Muslim self-rule in Asia's bastion of Catholicism.

A military statement said the soldiers were "fired upon by unidentified armed personalities" in Basilan island, triggering a firefight that left two soldiers dead and 12 others wounded.

The commander of the army unit, Brigadier General Alvin Luzon, said Thursday MILF gunmen attacked the troops who had been dispatched to "provide area security" to a United Nations team that was to visit a development project in the former MILF stronghold.

The UN visit was later aborted due to the firefight, he added.

The UN country office in the Philippines did not immediately respond to AFP's request for comment.

The peace treaty had led to the creation of a self-rule area in a Muslim-populated region in the southern Philippines, now run by Chief Minister Ahod Ebrahim, the former MILF chief.

However the process of decommissioning the weapons of thousands of MILF fighters following a lengthy armed campaign that left thousands dead is yet to be completed.

Ebrahim said in a statement sent to AFP that the regional Bangsamoro government -- which includes the island province of Basilan -- was "deeply saddened by the unfortunate encounter" with MILF members.

He urged all parties to "remain calm as we work towards addressing this incident through appropriate channels", while stressing the regional government "remains steadfast in its commitment to the full implementation" of the peace treaty.

Philippine Army commander Lieutenant General Roy Galido condemned the attack and said his forces are "working closely with local government units and law enforcement agencies to ensure that the perpetrators of this treacherous act face the full consequences of their actions".