WASHINGTON — U.S. airstrikes bombarded an al-Shabab training camp in Somalia on Saturday, killing more than 150 militant fighters who were preparing to launch a large-scale attack, likely against African or U.S. personnel, the Pentagon said Monday.

Multiple drones and manned aircraft launched missiles and bombs on the site, called Raso Camp, which the U.S. had been watching for several weeks, said Navy Capt. Jeff Davis, a Pentagon spokesman.

News of the attack comes as the White House announced Monday that it will disclose how many people have been killed by American drones and other counterterrorism strikes since 2009, when President Obama took office.

Lisa Monaco, Obama’s counterterrorism and homeland security adviser, said the report will be released “in the coming weeks,” casting it as part of a commitment to transparency for U.S. actions overseas. Monaco said the figures would be disclosed annually in the future, although it will ultimately be up to Obama’s successor to decide whether to continue the practice.

The report will include both combatants and civilians the U.S. believes have died in strikes. It won’t cover major warzones such as Iraq, Syria and Afghanistan, but will focus on strikes against extremist targets in other regions such as Pakistan, Libya, Yemen, Somalia and other locations in North Africa.

The Pentagon on Monday provided some details about the Somalia strike, which happened during the early evening there. Davis said it appeared that the training was about to come to an end, and the operational phase of a suspected attack was about to start. Military forces from the U.S. and the African Union Mission in Somalia are routinely working in the country, and Davis said they could have been the targets of al-Shabab’s planned attack.

The camp was destroyed, Davis said, adding that the U.S. believes there were no civilian casualties. He said the U.S. estimated that as many as 200 fighters had been at the camp, including a number of trainers.