A US air strike in Afghanistan has killed a senior Al Qaeda commander in charge of the group's suicide bombings, the Pentagon says.

The attack, which occurred in Paktika province on July 11, killed Abu Khalil al-Sudani, a "high-ranking Al Qaeda operational commander", the US military said in a statement released to reporters in Iraq who were travelling with US defence secretary Ashton Carter.

"Al-Sudani was one of three known violent extremists killed in the strike. The death of al-Sudani will further degrade Al Qaeda operations across the globe," the statement said.

The Pentagon described Sudani as a senior member of the group's "shura", or council, and head of Al Qaeda's suicide and explosive operations.

It said he was directly linked to plotting attacks against the United States.

"He also directed operations against coalition, Afghan and Pakistani forces, and maintained a close association with Ayman al-Zawahiri, Al Qaeda's leader," the statement said.

Mr Carter said the killing of al-Sudani underscored the work done by General John Campbell, the commander of NATO forces in Afghanistan, and his troops "to take the fight to Al Qaeda".

"We will continue to counter violent extremism in the region and the world," Mr Carter said in a statement.

Already struggling with the rise of rival jihadists from the Islamic State group, Al Qaeda has suffered a series of setbacks in recent months with several commanders reported killed.

The death of Nasir al-Wuhaysi was the heaviest blow to Al Qaeda since the death of Osama bin Laden. ( AFP )

Its second-in-command Nasir al-Wuhayshi, head of its powerful Yemeni branch, was killed in a US drone strike in June in the heaviest blow to the jihadist network since the death of Osama bin Laden.

Meanwhile in Syria, a US-led coalition air strike this month killed Muhsin al-Fadhli, the leader of Al Qaeda's offshoot Khorasan Group, which is accused of plotting attacks against the US and its allies.

Al-Fahdli was so trusted by Bin Laden's inner circle that he was among the few who knew in advance about the 9/11 attacks in New York.

US-led NATO forces ended their combat mission in Afghanistan in December, leaving local forces to battle militants alone, but a 13,000-strong residual force remains for training and counter-terrorism operations.

AFP/Reuters