WASHINGTON • The reported death of Islamic State in Iraq and Syria (ISIS) senior propagandist and strategist Abu Muhammad al-Adnani in a US drone strike in northern Syria casts in sharp relief the immediate challenge the terrorist group faces in replacing one of its pivotal founding members.

The attack, carried out by a military Reaper drone, also underscores the progress the military's most elite Special Operations commandos and the Central Intelligence Agency have made in the conflict's two years by using information from spies on the ground and sensors in the sky to target a growing number of ISIS leaders.

The US-led coalition has killed about 120 important ISIS officials and operators, including about a dozen of the group's top leaders, according to the Pentagon.

Still, ISIS has proved to be remarkably resilient, US officials and counterterrorism specialists say, noting that the group has succession plans to replace even its top leader, Abu Bakr al-Baghdadi, should he be killed. In the coming days, Baghdadi is likely to meet his shura, or council of advisers, in Raqqa, the group's self-proclaimed capital in Syria, to pick a replacement for Adnani, a 39-year-old Syrian, who had been believed to be Baghdadi's heir apparent.

Among the leading candidates to replace Adnani is Turki al-Binali, 31, who is believed to have been appointed the chief mufti, said Mr Cole Bunzel, a doctoral candidate at Princeton. A native of Bahrain, Binali is "an extremely talented speaker", said Mr Bunzel, who wrote a Brookings Institution paper on ISIS ideology.

It is unclear how the US tracked Adnani, but his death, if confirmed, highlights US agencies' ability to collect and coordinate information gathered from raids on ISIS safe houses. Such raids produce intelligence from cellphones and computer hard drives and other information that is combined with a network of spies and informants to put pressure on ISIS leaders.

Separately, Australia will expand its military action against ISIS in Syria and Iraq after amending its laws, Prime Minister Malcolm Turnbull said yesterday. Australian law currently allows only the targeting of people who play an active role in hostilities, which Mr Turnbull said was more restrictive than international law.

REUTERS