Militants have beheaded two Vietnamese sailors held hostage for eight months in the southern Philippines, the military said on Wednesday. Philippine troops found the remains of the two hostages early Wednesday (Jul 5) morning on the island of Basilan, a stronghold of the notorious Abu Sayyaf kidnap-for-ransom group, military spokeswoman Captain Jo-Ann Petinglay said. "Our troops found the headless bodies after local residents alerted us about the cadavers," Petinglay told reporters, adding that the heads were found beside the bodies. "This is a desperate measure of the Abu Sayyaf Group because they see they have no gains from their kidnap-for-ransom activity," Petinglay added. Abu Sayyaf, originally a loose network of militants formed in the 1990s with seed money from Osama bin Laden's Al-Qaeda network, has splintered into factions, with some continuing to engage in banditry and kidnappings. One faction has pledged allegiance to the Islamic State group, with members among those holding parts of Marawi, the largely Catholic nation's most important Islamic city. Militants continue to occupy parts of Marawi despite a US-backed military offensive there that has claimed more than 460 lives and displaced nearly 400,000 people since it began in May. The two Vietnamese were seized last November along with four other Vietnamese crew members of a vessel that was boarded by the militants off the southern region of Mindanao, the military said. One of the six crewmen was rescued last month and three remain in captivity, Petinglay said. Abu Sayyaf militants are holding a total of 22 hostages, including 16 foreigners, according to Petinglay. The Abu Sayyaf is known to behead its hostages unless ransom payments are made. German national Jurgen Kantner, 70, was beheaded in February after the kidnappers' demand for 30 million pesos (US$600,000) was not met. Last year, the group beheaded two Canadian hostages. FIGHTING ONGOING IN MARAWI Elsewhere in the southern region, intense fighting with a larger group of pro-Islamic State militants who seized Marawi City has dragged on for six weeks, killing more than 400 people, including 85 security forces. The dead include 39 civilians, but local officials said the number could be higher as intense fighting has denied authorities access to the center of the city. Military planes and helicopters have been dropping bombs and firing rockets on militants occupying high-rise buildings in the city's commercial center. Marines and army rangers fought militants in house-to-house combat to retake the city. Defence Secretary Delfin Lorenzana said there is pressure on the military to defeat the Islamist militants before a 60-day period of martial law expires on July 23, a day before the president delivers his state of the nation address in Congress. "In my estimate, the clearing operations will take at least a week," he said on Tuesday, adding that the enemy's resistance was waning as troops gain control of more strategic positions. Lorenzana said the Philippines last week sent a military plane to the United States to acquire an unspecified number and type of bombs and rockets intended to replenish the country's weapons stockpile, depleted by almost daily bombings in Marawi.