Somali Al-Shabaab terrorists
Somali Al-Shabaab terroristsReuters

The United States military on Monday carried out an airstrike against the Islamic terrorist group Al-Shabaab in Somalia, NBC News reported, but the Pentagon did not say whether the intended target, described only as a senior leader, was killed.

A U.S. official told NBC News that no ground forces were involved.

"At this time, we do not assess there to be any civilian or bystander casualties," Rear Adm. John Kirby, the Pentagon press secretary, said in a statement.

In September, the United States killed the Somali group’s leader, Ahmed Godane, in an airstrike in Somalia.

Since taking charge of Al-Shabaab in 2008, Godane had restyled the group as a global player in the Al-Qaeda network, carrying out bombings and suicide attacks in Somalia and elsewhere in the region, including the September 21, 2013, attack on the Westgate shopping mall in Nairobi, Kenya, that killed 67 people.

Godane publicly claimed responsibility for the Westgate attack, saying it was revenge for Kenyan and Western involvement in Somalia and noting its proximity to the anniversary of the September 11, 2001, attacks on the United States.

Godane's close associate, Ahmed Mohamed Amey, was killed by a U.S. airstrike last January.

Last month, Al-Shabaab murdered 28 people in an attack on a bus in Kenya's northeastern Mandera county, separating out the Muslims from the non-Muslims before shooting their victims in the head.