MANILA: Philippine officials asked lawmakers Tuesday not to withdraw their support from a new government peace deal with the country's largest Muslim rebel group after some insurgents were involved in a clash that killed 44 anti-terror police commandos.

The government's biggest single-day combat loss in recent memory shocked many and prompted at least two senators to withdraw their backing for a bill that would create a new Muslim autonomous region in the restive south under a peace deal signed last March.

Many more lawmakers and influential Roman Catholic bishops defended the deal.

Read: Philippines, Muslim rebels clinch peace deal

The Catholic Bishops Conference of the Philippines condemned the violence, but said it “cannot side with those who call for the discontinuance of peace talks,” said Archbishop Socrates Villegas, who heads the group.

President Benigno Aquino III's spokesman, Herminio Coloma, warned that abandoning peace efforts could usher in the return of an “old order characterised by warlordism, lawlessness, misuse of public funds and the near-total breakdown of governance. “

Aquino's peace talks with the 11,000-strong Moro Islamic Liberation Front, along with a cease-fire, have virtually ended major fighting in the south in the last four years.

The decades-old Muslim separatist insurrection has left about 150,000 dead and blocked progress in the country's most destitute regions.

The respite was shattered early Sunday when police commandos barged into a remote marshland area off southern Mamasapano town in Maguindanao province to hunt down Malaysian Zulkifli bin Hir, or Marwan, one of Southeast Asia's most-wanted terror suspects, and a top Filipino terror suspect, Abdul Basit Usman. Interior Secretary Mar Roxas said Marwan may have been killed in the raid but Usman escaped.

Efforts to verify Marwan's death were underway.

As the commandos withdrew, they came under fire from hard-line Muslim militants called the Bangsamoro Islamic Freedom Fighters.

Some of the policemen maneuvered away in the dark and became entangled in a “misencounter” with heavily armed Muslim rebels belonging to the Moro Islamic Liberation Front, according to Roxas.

When the fierce fighting ended, 44 commandos were dead and 12 others were wounded, national police Deputy Director General Leonardo Espina said. Some Muslim rebels said as many as 56 of the elite policemen died in the daylong clashes, which left about a dozen insurgents dead.

Moro rebel leader Mohagher Iqbal accused the police commandos of violating the cease-fire agreement, which requires government forces to coordinate anti-terror assaults and other law enforcement operations with the Moro insurgents to prevent accidental clashes.

Senior military officials said they also were unaware of the police offensive.

Despite the peace talks with the Moro rebel front, many security officials still nurture suspicions that some of its commanders may be harboring foreign terror suspects such as Marwan, prompting them to keep the insurgents unaware of anti-terror raids in the past.

Roxas announced Tuesday that the head of the police commandos, Getulio Napenas, has been removed from his post. He said Napenas did not clear the anti-terror assault with him or Espina. But the huge body count sparked outrage and placed the government in a dilemma.

The government ordered an investigation into the fighting but praised the slain commandos as “fallen heroes” who will be accorded full military honors and combat medals.

Flags were flown at half-staff in police and military camps as the country mourned. Sen. Alan Cayetano, who introduced the bill that would create a more powerful and potentially larger autonomous region for minority Muslims in the south, withdrew his support of the legislation to protest the killings of the policemen.

“I'm disgusted,” Cayetano said. “With the recent events involving the slaughter of our policemen ... there is reason to doubt the commitment of the Moro Islamic Liberation Front to a framework for peace and development.“

But Senate President Franklin Drilon and most other lawmakers defended the Muslim autonomy bill. “We should not allow this unfortunate incident and the deaths of our policemen, condemnable as it is, to stand in the way of efforts to bring lasting and genuine peace and development,” Drilon said. “It must all the more strengthen our desire and resolve for peace.“

Despite the huge number of police casualties, officials said, the peace process actually worked. At the height of the fighting, members of a cease-fire committee and a Malaysian-led peacekeeping contingent intervened and pacified the combatants.

The Moro rebels withdrew to a safe distance, allowing policemen and villagers to travel to the battle scene to retrieve the slain commandos, many of whom were stripped of their belongings and assault rifles.

The country's search for peace in its restive south has survived past upheavals.

In 2011, army troops seeking to arrest a fugitive rebel commander clashed with Moro Islamic Liberation Front forces in southern Al Barka town, sparking a clash that killed 19 soldiers, one of the previous largest army losses in a single clash.

The killings sparked calls for Aquino to break a truce and order a major offensive against the rebels. Aquino ordered an investigation but rejected the calls and decided to pursue talks, a decision backed by the United States, Britain and Japan, countries which have backed yearslong peace negotiations.

The Malaysia-brokered talks led to the signing of the Muslim autonomy deal last year.