By Hader Glang

ZAMBOANGA CITY, the Philippines

Seven soldiers were wounded in the Philippines’ Muslim south Wednesday morning after suspected Daesh-linked militants threw a grenade at their truck, according to the military.

Maj. Filemon Tan Jr., Western Mindanao Command spokesman, told reporters that the attack in Jolo island of Sulu province came days after the Abu Sayyaf group set a June 13 deadline for executing foreign hostages if a ransom is not paid.

“Initial investigation revealed the soldiers were about to go back to their camp from Jolo port after buying supplies and fetching their companions, and upon reaching Plaza Marina, a grenade [was] hurled at their truck and exploded," he said in nearby Zamboanga City.

Security forces from the Jolo Municipal Police Station backed by regional public safety battalion units rushed to the scene, where they recovered part of a grenade.

The soldiers, who sustained minor injuries, were rushed to a Jolo hospital for immediate treatment, before being airlifted to a military hospital at Camp Navarro in Zamboanga City.

Tan also reiterated that the Armed Forces of the Philippines do not heed ultimatums from criminals and deadlines imposed by the Abu Sayyaf, against whom a focused military operation is ongoing.

"The safety of the kidnap victims though is our primary concern. We will do our best to accomplish our mission," Tan said.

On April 25, the Abu Sayyaf beheaded 68-year-old Canadian John Ridsdel after a 300-million peso (more than $6 million) ransom failed to be paid.

Earlier this week, the military said it was verifying a video in which militants threaten to execute another Canadian and a Norwegian, who were abducted alongside Ridsdel and a Filipina in September off southern Mindanao island.

In the video, the foreigners warn that they will be beheaded unless a 600 million peso ($12.9 million) ransom is paid by 3 p.m. (0700GMT) on June 13.

The Abu Sayyaf is believed to still be holding several other captives, including four Malaysian crew seized from a vessel in early April, and a Dutch national kidnapped more than three years ago in Tawi-Tawi island province.

Since 1991, the group -- armed with mostly improvised explosive devices, mortars and automatic rifles -- has carried out bombings, kidnappings, assassinations and extortions in a self-determined fight for an independent province in the Philippines.

It is notorious for beheading victims after ransoms have failed to be paid for their release.