MANILA: Hundreds of extra troops have been deployed in the southern Philippines after gunmen believed linked to a local politician kidnapped and killed at least 22 people, a military spokesman said Tuesday.

One battalion of about 500 infantrymen was sent to Maguindanao province on Mindanao island after Monday's massacre, military spokesman Lieutenant-Colonel Romeo Brawner told AFP.

Supporters of a prominent local politician in Maguindanao province and local journalists were among those murdered, with some of them beheaded and mutilated, the military and relatives said.

Brawner said the unit, which adds to about 3,000 troops already based in the area, was under orders to arrest the followers of local politician Andal Ampatuan, who is accused of being behind the abduction and subsequent murders.

"We maintain the Ampatuans are the suspects," Brawner said.

He said the troops were also tasked with finding at least 20 other people who were abducted and remain missing.

"We believe more bodies are buried in the ground and we are trying to recover them," Brawner said earlier in an interview with the ABS-CBN television network.

The murders occurred after gunmen linked to Maguindanao governor Ampatuan abducted members of a rival political clan and the local reporters who had been travelling in a convoy on Monday morning, according to Brawner.

The leader of the rival political clan that was attacked, Esmael Mangudadatu, had been meaning to nominate for the governorship of the mainly Muslim Maguindanao province for next year's elections.

He was not in the group of about 40 people that was abducted, apparently after he had received warnings from Ampatuan's people not to register in the polls.

But Mangudadatu's wife was in the group and had been intending to lodge his nomination for him.

The Mangudadatu family is known to have a long-running feud with the Ampatuans, who police say are known to control their own private army.

Mangudadatu said his wife was among those killed and that many of the victims had been mutilated.

"Their private parts were showing, their heads were crushed, they were mutilated," he told ABS-CBN, as he blamed the Ampatuan clan for the killings.

Before the bodies were recovered, Brawner confirmed gunmen linked to Ampatuan had abducted the group.

Although he would not say afterwards that the Ampatuan clan was responsible for the killings, he said it was a strong suspicion.

"Right now that's the angle we're looking at. The abduction of the Mangudadato family members by the elements of the Ampatuans is due to a political feud," Brawner said.

Revenge killings and clashes among rival political clans are common in Maguindanao and other parts of the strife-torn southern Mindanao island, where unlicensed firearms proliferate and a Muslim insurgency has waged for decades.

The Philippines is also regarded as one of the most dangerous places in the world for journalists.

However, the scale of Monday's slaughter sent immediate shock waves through the country.

"This is a gruesome massacre of civilians unequalled in recent history," said Jess Dureza, President Gloria Arroyo's adviser on Mindanao island.

"There must be a total stop to this senseless violence. I strongly recommend that a state of emergency be imposed in the area and everyone be disarmed. Anything less will not work."

Arroyo's office later released a statement saying no effort would be spared to bring justice to the victims. Related article: Philippine govt vows justice

"Civilised society has no place for this kind of violence," the statement said.

Amid reports from media groups that as many as 12 of the victims may have been journalists, the National Press Club of the Philippines also expressed outrage.

"We are condemning this brutal incident. We have this culture of impunity in Mindanao that needs to change," club president Benny Antiporda said.

Jaime Espina, a spokesman for the National Union of Journalists of the Philippines (NUJP), called it "a direct challenge to our efforts to strengthen democracy in this country".

Before the reports of the massacre, Brawner said the leader of the militiamen who staged the kidnapping was one of Ampatuan's sons.

Esmael Mangudadatu's brother, Khdadafeh, also said Ampatuan had warned Esmael not to register for the elections.

"His son, Andal Ampatuan Jnr, is supposed to run for governor and he had already made an earlier announcement that we would be killed if (Esmael) filed the candidacy for governor," Khdadafeh told AFP.