Philippine soldiers scour a small village for armed men sighted in Ampatuan town in Maguindanao on December 7, 2009, after military troops found a cache of weapons buried at the back of the municipal hall. (AFP Photo)

SHARIFF AGUAK, Philippines, December 8, 2009 (AFP) - The Philippine military is confident of quashing a rogue politician's militia in the troubled south, but worried the offensive is creating power vacuums from which more fearsome forces could emerge.

President Gloria Arroyo imposed martial rule and deployed thousands of troops in Maguindanao province to disarm a former ally who became an enemy of the state after his Muslim clan was accused of massacring 57 people last month.

However the move came partly at the expense of a military operation against the communist New People's Army, which has been waging a long insurgency across the Philippines that has claimed 3,000 lives in the past eight years alone.

"This has disrupted our operations against the NPA," Lieutenant-General Reymundo Ferrer, the martial law military administrator of Maguindanao, told reporters in the provincial capital of Shariff Aguak on Monday.

To combat the estimated 3,000 gunmen loyal to former Maguindanao governor Andal Ampatuan Sr., who the government says will soon be charged with rebellion, Ferrer pulled in thousands of troops from other parts of country.

One battalion of about 500 soldiers came from Samar in the central Philippines, a New People's Army stronghold.

Another battalion was shifted from Davao, a major city on Mindanao island in the southern Philippines where communist guerrillas are also known to operate.

Arroyo has declared a goal of ending the guerrilla threat in Davao by the end of this year.

"(But) in the case of the Davao region it appears we will not be able to achieve that this year," he said.

The government has insisted it should soon be able to dismantle Ampatuan's militia of about 3,000 gunmen, allowing the martial law imposed late on Friday night to be quickly lifted.

Ampatuan Sr. and four other senior clan members have already been arrested in martial law raids.

One his sons, Andal Ampatuan Jr., was in custody having been charged with 25 counts of murder over the November 23 massacre.

Ampatuan Jnr allegedly led 100 of his gunmen in abducting and killing the victims, who included female relatives of a rival politician plus a group of journalists travelling in a convoy with them.

The rival said the attack was meant to stop him from running for governor in next year's elections.

The Ampatuans are one of several clans whom Arroyo's government has embraced politically as part of a strategy to contain a Muslim insurgency that has waged across Maguindanao and other parts of Mindanao island since the 1970s.

The insurgency has claimed at least 150,000 lives, the military says.

The government allowed the Ampatuans and other clans to build up their own security forces to help overstretched military and police units on Mindanao.

Against this backdrop, Defence Secretary Norberto Gonzales said the security problems in Maguindanao would not end with the disarming of the Ampatuan militia.

He said there was a danger that some of the Ampatuan gunmen would enter into an alliance with the Moro Islamic Liberation Front (MILF), the Muslim insurgents who are currently the clan's enemies.

Gonzales also said the MILF and other Ampatuan enemies would likely be watching with interest as the Ampatuans lost land they had taken control of during their time in power.

"Now we're going after (the Ampatuan militia), so they left their land and this will be taken over by another party, so that is another problem," Gonzales told reporters in Shariff Aguak on Monday.

"The military must settle land dispute issues because once our armed forces pull out there will be another land grab and there will be trouble again."

Gonzales said authorities also feared the removal of Ampatuan Snr, the most powerful politician in Maguindanao, would rekindle family disputes in a region where Muslim clans engage in vendetta killings that last through generations.

"We are looking at this problem because that (clan wars) is one of the aftermaths that we have to guard against," he said.

Ferrer also warned clan wars were a problem, exacerbated by the easy manner in which those in power could accumulate weapons.