At least 17 people, including women and children, were killed by Abu Sayyaf gunmen in southern Philippines on Monday.

The militants attacked two vans carrying civilians who were travelling to visit relatives and celebrate the end of the Muslim fasting month of Ramadan, military officials said, according to an Associated Press report. The attack was carried out near a coastal village in Talipao, on the island of Mindanao, by about 50 Abu Sayyaf militants armed with assault rifles, Marine Brig. Gen. Martin Pinto and other military officials reportedly said.

Fifteen people were killed when the militants opened fire on the vans, while two died at a hospital. Eleven other villagers were injured in the attack. The cause of the attack was not yet known but a family feud involving some of the militants could be the reason, Pinto reportedly said.

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    Abu Sayyaf rebels are seen in the Philippines in this video grab made available February 6, 2009. Photo: REUTERS/Philippine National Red Cross via Reuters TV
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    Family members cry on the coffin of a soldier, killed in a battle with Abu Sayyaf Muslim rebels on nearby Basilan island, during a funeral wake in a military camp in Zamboanga city August 14, 2009. Photo: REUTERS/Erik de Castro
  • seized camp of Abu Sayyaf militants
    Filipino soldiers gather at a seized camp of Abu Sayyaf militants on Jolo island in southern Philippines Sept., 21, 2009. Photo: Reuters/Handout/Western Mindanao Command
  • philipine muslims
    Filipino Muslims pray during the celebration of Eid al-Fitr, marking the end of the holy month of Ramadan, early morning at a public park in Manila July 28, 2014. Photo: REUTERS/Erik De Castro
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    Filipino religious group and Red Cross workers attend an interfaith rally in Quezon city hall, metro Manila February 25, 2009 to ask for the immediate and safe release of 3 international Red Cross workers who were abducted by Abu Sayyaf rebels in the southern Philippines in January. Photo: REUTERS/Romeo Ranoco

Among those killed were four members of a Talipao civilian security force called Barangay Police Action Team, AP reported, adding that, in recent months, the civilian security force had helped the military fight the militants, who are active in the country's Muslim-dominated south.

Abu Sayyaf, which was formed in the southern Philippines during the early 1990s, consists of about 300 armed fighters divided into many factions. The group has been pushed back to the jungles and has largely been crippled by a U.S.-backed Philippine military offensive, forcing it to survive mainly on ransoms from kidnappings in the region, the report said. The group currently holds about 10 hostages, which include two German tourists kidnapped in April and two other European tourists who were kidnapped two years ago, AP reported.

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In a country where the majority population is Roman Catholic, Abu Sayyaf is one of four smaller Islamist insurgent groups that did not accept a peace deal signed by the Philippine government in March with the Moro Islamic Liberation Front -- the country's largest rebel group with 11,000 members. The Islamist groups demand the creation of a large autonomous region for the country‚Äôs Muslim minority in the south.