MANILA: Abu Sayyaf gunmen attacked Filipino civilians traveling to celebrate the end of Ramadan with their families on Monday, killing 21, including at least six children, in a brazen road attack that was the bloodiest in recent years by the violent militant group, police and military officials said.

Eleven other civilians were wounded as the group traveled in two vans in a coastal village in Talipao town in predominantly Muslim Sulu province, where the militants have survived in jungle camps despite years of US-backed Philippine military offensives.

About 40 to 50 Abu Sayyaf militants armed with assault rifles opened fire on the vans, marine Brig. Gen. Martin Pinto and other military officials said. The motive was not immediately clear, but Pinto said some of the dead belonged to a civilian security force and were engaged in a clan feud with the Abu Sayyaf.

Violent clan wars, known as “rido,” have complicated security worries in the country’s south, which is already mired in decades-long Muslim rebellions.

Officials said they were pursuing the militants after the attack, but there’s no word yet if any of them have been killed or captured.

Among those killed in the attack were at least four members of a Talipao civilian security force called Barangay Police Action Team that has been helping the military fight the jungle-based militants in recent months, Pinto said.

Armed forces spokesman Lt. Col. Ramon Zagala condemned “this heinous atrocity that victimized innocent civilians,” adding that the military “will continue its pursuit operations until those responsible are brought to justice.” “This attack cannot be justified by any ideology and shows the Abu Sayyaf’s terroristic nature,” Zagala said.

Six of the dead were aged 2 to 15 and four of the wounded are children, including a 3-year-old boy, police and military reports showed. An 83-year-old man was among the dead.