American commandos have killed senior IS leader Abu Sayyaf in a covert operation in war-torn Syria, the US government said on Saturday.
John Ridsdel, 68, was one of four tourists captured by Abu Sayyaf militants in the Philippines in September 2015.
The blast occurred in the centre of Davao, close to one of the city's top hotels and a major university.
After 14 months in captivity, an Indian national abducted by Al Qaeda linked Abu Sayyaf militants in southern Philippines on Friday dramatically escaped from his captors while they were sleeping after fasting for Ramzan.
Interior Secretary Angelo Reyes confirmed that Abu Sayyaf commander -- Ghalib Andang, also known as "Commander Robot," and Alhamser Mantad Limbong, alias "Commander Kosovo" were among those killed in the attack on the high-security detention complex.
Wives of top Islamic State leaders, including its chief Abu Bakr al-Baghdadi, play an important role in passing information to one another and then to their spouses to avoid electronic intercepts, according to a media report.
A bomb exploded Monday at a crowded market killing 13 people in the latest deadly attack in southern Philippines, officials said.
The stand off began after some 10 prisoners at the high security Camp Bagong Diwa snatched weapons from their guards and started shooting, killing three guards and a prisoner.
The Philippines army battles terrorists backed by Islamic State in the first major military encounter with Islamists in that part of the world.
The US has deployed its elite counter-terrorism unit Delta Force for covert operations in Iraq to capture or kill high-ranking Islamic State operatives and gather intelligence, according to a media report.
Any attempt to defang Islamic State must first cut off its main sources of funding, especially its revenue from oil sales, extortion and crime, ransom payments, and support from foreign donors. This will also be need to be backed up by efficient forces on the ground.