Members of the breakaway Muslim separatist group Bangsamoro Islamic Freedom Fighters (BIFF) stand guard during a clandestine press conference in the town of Datu Unsay, sothern Maguindanao province in the Philippines, on August 28, 2011
More than 40 Philippine police commandos were killed in an 11-hour firefight with Muslim rebels which erupted while they were chasing one of the region's most wanted militants, police said Monday.
The clash -- which broke out despite a peace pact with the main rebel group -- was "the single largest loss of life in recent memory by our security forces", said interior minister Manuel Roxas.
A total of 43 commandos were killed Sunday in the remote town of Mamasapano, a known rebel stronghold, on Mindanao island in the south, the national police chief Leonardo Espina told a news conference.
Regional police spokeswoman Judith Ambong told AFP separately the bodies of 49 policemen were recovered.
Eleven police were injured but there was no information on any Muslim rebel casualties.
Almost 400 police commandos swooped before dawn on the hideout of the Bangsamoro Islamic Freedom Fighters (BIFF), a splinter group which rejects the peace pact, in search of Zulkifli bin Hir.
Roxas said police claimed to have killed Zulkifli, a bombmaker for the Jemaah Islamiyah (JI) group which staged the 2002 Bali bombings and other deadly attacks.
He is among the United States' most wanted militants, with a $5 million bounty for his capture.
But as the commandos were leaving they encountered the Moro Islamic Liberation Front (MILF), sparking a "misencounter", he said.
The 10,000-strong MILF, the main Muslim rebel group in the south, signed a peace treaty with the government in March last year.
The BIFF, a breakaway faction of several hundred Muslim gunmen, was not part of the deal.
President Benigno Aquino ordered an investigation into the incident, a major test of the accord intended to end a 40-year insurgency that has claimed tens of thousands of lives.
The MILF said police did not coordinate the operation as required under the ceasefire accord.
"There will be an impact but we are hopeful and confident that this will not derail the peace talks," Roxas said.
He said Zulkifli was believed killed based on pictures from the encounter site, but his body had not been recovered or positively identified.
The Malaysian is the most prominent of the 10 to 12 foreign JI members believed hiding in the Philippines. He slipped into the southern region in 2003 and has since been training local militants, according to the military.
- 'Big problem' -
Roxas said the leader of the BIFF, Basit Usman, escaped. He had been blamed for recent bomb attacks in the south.
"This is going to be a big problem," the MILF's chief peace negotiator Mohagher Iqbal told AFP when asked how the fighting would affect the peace process, adding that it still stood.
The MILF had agreed to end its revolt in the mainly Catholic nation in exchange for a proposed law now being debated in parliament that would give minority Muslims self-rule in several southern provinces.
The rebels were scheduled to start disarming at the start of this year.
"This is the first encounter between the MILF and (government forces) this year. Hopefully, this will be the last," Iqbal said.
"We are committed (to the peace process). For the MILF, the ceasefire still holds," he said.
The rebel group's vice chairman, Ghazali Jaafar, said the peace treaty signed last March was the only solution to the conflict.
Sunday's bloodbath highlighted "security challenges" but nonetheless strengthened the resolve of negotiators, government peace panel chairperson Miriam Coronel-Ferrer said in a statement.
Over 1,000 people displaced by the violence have begun returning to their homes after the fighting stopped Sunday afternoon, Mamasapano town mayor Tahirodin Benzar Ampatuan said.
The firefight was only the second since the ceasefire. Two soldiers and 18 Muslim gunmen were killed in a clash on the southern island of Basilan in April 2014.
Since the peace accord was signed, authorities have been hot on the trail of the BIFF. The group pledged allegiance to Islamic State fighters in Iraq and Syria last year.