Ibrahim al-Asiri is thought to have been involved in numerous plots including one on Christmas Day 2009, when a Nigerian man attempted to set off plastic explosives sewn to his underwear on a flight from Amsterdam to Detroit.

"We are confident he was killed late last year," the official said on condition of anonymity.

According to a UN team that tracks terror groups in the Middle East, some Security Council members "report that explosives expert Ibrahim al-Asiri may have been killed during the second half of 2017."

"Given al-Asiri's past role in plots against aviation, this would represent a serious blow to operational capability," notes the report, released last week.

The Pentagon said it had no information it could provide.

Asiri, a Saudi, belonged to Al-Qaeda in the Arabian Peninsula, which is based in Yemen and is the target of ongoing US counter-terror operations.

Asiri, a one-time chemistry student also known as Abu Saleh, was on several most-wanted lists and had survived repeated US attempts to kill him.

He specialized in building non-metallic explosives, often using Pentaerythritol tetranitrate, or PETN, and chemical detonators.

Asiri was thought to have been involved in making a bomb for the failed 2009 Christmas Day plot, and an attempt to send parcel bombs containing PETN hidden in printer ink cartridges from Yemen to Chicago in 2010.

He is also believed to have designed a bomb used by his brother Abdullah, who died in a failed suicide attack on Saudi Arabia's deputy interior minister in 2009.

In the Christmas Day plot, Umar Farouk Abdulmutallab attempted to set off plastic explosives sewn to his underwear on a flight from Amsterdam to Detroit.

He failed to detonate the explosives, was subdued by a passenger and is now serving a life sentence in the United States.