At least 13 people have been killed by a bomb blast in the southern Philippine island of Mindanao. Another 12 were injured.

The army said that Islamic militants had carried out the attack in the town of Datu Piang, in which a mortar was detonated by remote control as Mayor Saudie Ampatuan walked past.

Only the Moro Islamic Liberation Front "is capable of making powerful home-made bombs", army spokesman Major Julieto Ando told The Associated Press news agency.

MILF spokesman Eid Kabalu denied responsibility for the attack, saying he had relatives among the injured.

The army say they have in custody a witness who saw a suspected follower of an MILF leader plant the bomb.

Blast

Ampatuan was caught in the blast as he returned home from a ceremony in honour of a dead relative.

He died in hospital on injuries to his head and abdomen.

The mayor is not our enemy Eid Kabalu, MILF spokesman

In addition to the mayor - a Muslim - the dead included a town councillor, treasurer and a bodyguard, the army said.

The army deployed about 500 soldiers to the region in response to the attack, Major Ando said, adding that MILF fighters had been spotted in the area.

MILF spokesman Kabalu said the movement had no quarrel with the mayor.

"There is no reason for us to do that because the mayor is not our enemy," he said.

Ampatuan survived an MILF attack along with his father, the governor of Mindanao's Maguindanao province, earlier in the year.

Brother killed

His younger brother, his brother's wife and friend were killed on Saturday following an incident at a disco.

His family is reported to have retaliated against two people related to suspects in the attacks.

The army has sent more troops to the area

Army spokesman Ando said Tuedsay's killing of the mayor seems not to be connected with the killing of his brother at the weekend.

The southern Philippines has been a scene of separatist conflict for 30 years, led by Muslim rebels in the predominantly Catholic country.

The MILF have signed a cease-fire and peace talks with the government are expected to resume in Malaysia next month.

The group denies any connection to the Muslim militant Abu Sayyaf group, which has been accused of links with the al-Qaeda network.