WASHINGTON - U.S. air strikes bombarded an al-Shabab training camp in Somalia Saturday, killing more than 150 militants 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 United States 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.

"We know that not only is greater transparency the right thing to do, it is the best way to maintain the legitimacy of our counterterrorism actions and the broad support of our allies," Monaco said at the Council on Foreign Relations.

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 (AMISOM) are routinely working in the country, and Davis said they could have been the targets of al-Shabab's planned attack.

The camp, located about 120 miles north of Mogadishu, 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.

The al-Qaeda-linked al-Shabab has been linked to a number of attacks, including the detonation of a bomb aboard a commercial passenger jet last month that forced the plane to make an emergency landing in Mogadishu.

While sketchy details often emerge about individual drone strikes, the full scope of the U.S. drone program - conducted by both the Defense Department and the CIA - has long been shrouded from view. And the new report is not likely to answer all of the questions.