American warplanes on Saturday struck a training camp in Somalia belonging to the Islamist militant group the Shabab, the Pentagon said, killing about 150 fighters who United States officials said were preparing an attack against American troops and their regional allies in East Africa, reports The New York Times.

The strikes at a training facility in Rasa, about 120 miles north of Mogadishu, came as the Shabab fighters were nearing the end of “training for a large-scale attack” on forces belonging to the African Union in Somalia, officials said.

They were bombed during what United States officials said they believed was a graduation ceremony, and the warplanes dropped a number of precision-guided bombs and missiles on them. “They were standing outdoors in formation,” one official said.

The United States has a number of Special Operations forces in Somalia, and Defense Department officials said they were also believed to have been targets of the planned attacks.

The Shabab fighters killed in the strikes were “nearing the completion of the end of their training,” said Capt. Jeff Davis, a Pentagon spokesman. He said the strikes “will degrade Al Shabab’s ability” to attack its neighbors and the West.

The latest strikes come as East Africa analysts say that the Shabab, the group responsible for the 2013 attack on the Westgate mall in Kenya, is making a comeback after American strikes killed the group’s top leadership in 2014. Last month, the Shabab claimed responsibility for an attack on a popular hotel and a public garden in Mogadishu that killed 10 people and injured more than 25 others.

In the past two months, Shabab militants have killed more than 150 people, including Kenyan soldiers stationed at a remote desert outpost and beachcombers in Mogadishu. In addition, the group has claimed responsibility for a bomb placed aboard a Somali jetliner that tore a hole through the fuselage.

Pentagon officials would not say how they knew that the Shabab fighters killed on Saturday were training for an attack on United States and African Union forces, but the militant group is believed to be under heavy American surveillance.

Some experts say that the Shabab, an Al Qaeda affiliate, is in a competition with the Islamic State to show that it has not been eclipsed.