At least 21 rebels have been killed following fierce fighting between two rival groups in the southern Philippine island of Sulu, according to the police and military.
A Philippine police spokesman said on Monday that 13 members of the al-Qaeda-affiliated Abu Sayyaf Group (ASG) were killed, while eight fighters were confirmed dead from the Moro National Liberation Front (MNLF).
Antonio Freyra, Sulu provincial police chief, told the local media that the ASG had beheaded four of the MNLF rebels in the town of Patikul.
Freyra was also quoted as saying that the fighting was still going, forcing hundreds of civilians to flee in the predominantly Muslim province.
Roughly 200 ASG members and between 700 to 1,000 MNLF fighters were involved in the clashes.
In a statement sent to the press, a Philippine army spokesman said a marine brigade has been deployed to contain the violence.
"The situation is now under control and [army] troopers are now working closely in assisting" the displaced families, Colonel Arnulfo Burgos said.
It was the first major bloody confrontation between the two groups, which have co-existed for years and at times were suspected of collaborating on kidnappings and backing each other in clashes against government troops.
The larger MNLF group had signed an autonomy deal with the government in 1996.
The breakaway ASG was founded in 1991 by Abdurajak Abubakar Janjalani, who fought against the Russians in Afghanistan in the 1980s.
The fighting erupted on Saturday night, following the release of two Filipino television crew members accompanying Jordanian journalist Baker Atyani, who remains a captive of the ASG.
Atyani, who interviewed Osama bin Laden three months before 9/11 attacks, travelled to Sulu with his Manila-based crew to work on a documentary about the country's volatile south and possibly interview ASG fighters.
Military officials said ASG had demanded $3.1m for the release of Atyani.
The Abu Sayyaf is also holding Dutch tourist Elwold Horn, his Swiss companion Lorenzo Vinciguerra, a Japanese treasure hunter and a Malaysian national.
A former Australian soldier was separately being held by the Abu Sayyaf either on nearby Basilan island or the Zamboanga peninsula, also in the south.
Meanwhile, the two released Filipinos kidnapped with Atyani said they were told to walk away from a jungle hideout to a highway on Saturday evening.
Rolando Letrero and Ramelito Vela said they had no clue why they were released.
The captors reportedly gave Vela a horse as he was unable to walk due to a swollen leg, local media reported.