By Hader Glang

ZAMBOANGA CITY, the Philippines

Eight fishermen have been killed in an attack by suspected pirates off troubled southern Mindanao island, according to the Philippines’ military Tuesday.

Maj. Filemon Tan Jr., Western Mindanao Command spokesman, said in a statement that the fatalities were among a crew of 15 on a fishing boat that was strafed off Zamboanga City late Monday.

"Five armed men attacked a fishing boat, killing eight of the 15 crewmen on the spot, while the others jumped off the said boat and survived," he said.

Tan added that two of the men who jumped off the vessel swam to safety and have been rescued, while the other five remain missing.

He underlined that the military's joint task force is closely monitoring developments in the region’s piracy-ridden seawaters.

According to the Zamboanga Task Force’s commander, Colonel Juvymax Uy, search and rescue operations for those missing are underway.

Kidnap-for-ransom gangs operating in the nearby Sulu and Celebes seas are known to hand over their captives to the Abu Sayyaf militant group and negotiate for a ransom that, if paid, is shared with the group.

Monday's attack came two months after gunmen seized six Vietnamese crew members from a vessel off the island province of Basilan -- a stronghold of the Daesh-affiliated Abu Sayyaf.