London – Terror group al-Qaeda confirmed the death of its believed deputy-leader Abu Khayr al-Masri who died in an air strike staged by the US-led international coalition in northwestern Syria.

The senior commander, considered a grave loss to the ultra-hardline group, was killed in a series of air raids that had been targeting Syria’s Idlib province. Pentagon has stepped up airstrikes against top Qaeda operatives in the last two months, killing several important figures.

Yemen-based Qaeda offshoot which goes by al-Qaeda in the Arabian Peninsula (AQAP) had confirmed the death of Masri, broadcasting its condolences to the mother branch.

AQAP took advantage of Masri’s death to advance its anti-US propaganda among supporters, saying that the downfall of the chief commander in Syria is another crime committed by what it calls a ‘crusader’ coalition, in reference to the US-led coalition.

The British-based Syrian Observatory for Human Rights said that coalition air forces carried out a strike on February 26 against al-Mastumah, a village in Idlib. Islamist groups such as the ex-Qaeda affiliate Jabhat Fateh al-Sham, formerly known as al-Nusra, control the village.

Masri, 59, was an explosives expert and married to the daughter of Qaeda’s notorious Osama bin Laden.

Charles Lister, a senior fellow at the Middle East Institute and an expert on the war in Syria, said in an email that the death of Mr. Masri was the most significant blow to Qaeda’s global network since the killing of Nasir al-Wuhayshi, Qaeda’s No. 2 official at the time, in a drone strike in Yemen in June 2015.

Wuhayshi, AQAP’s former leader, was among Yemen’s and Saudi Arabia’s most wanted fugitives. In October 2014, the US State Department increased the reward for any information leading to the capture or killing of al-Wuhayshi to US$10 million, the same as ISIS leader Abu Bakr al-Baghdadi.

Lister says that Masri’s death will very likely provoke a response from the terror group, whether inside Syria or anywhere across the world.

Qaeda’s mouthpieces carried reports of the attack on Sunday, including photographs of the vehicle purportedly hit by the drone.

Masri was Egyptian and Abdullah Muhammad Rajab Abd al-Rahman was his birth name. A veteran of extremist conflicts in Afghanistan, Bosnia, Egypt and Pakistan, he was a longtime member of Qaeda’s highly secretive Shura Council, and he was the terrorist group’s key intermediary with its affiliates and other extremist groups across the world, Lister said.