TERRORISM

US strike 'most likely' killed al-Shabab leader responsible for American deaths, official says

FILE - In this Thursday, Feb. 17, 2011 file photo, al-Shabab fighters march with their weapons during military exercises on the outskirts of Mogadishu, Somalia.  A U.S. drone strike in Somalia has targeted a key leader of the al-Shabab militant group who was involved in two attacks in Mogadishu more than a year ago that killed more than 30 people, at least three Americans among them, the Pentagon said Friday, April 1, 2016. Several U.S. officials said he and two others were killed. Hassan Ali Dhoore was targeted in the airstrike Thursday, but the U.S. military was still assessing the results, Pentagon spokesman Peter Cook said in a statement. (AP Photo/Mohamed Sheikh Nor, File)

FILE - In this Thursday, Feb. 17, 2011 file photo, al-Shabab fighters march with their weapons during military exercises on the outskirts of Mogadishu, Somalia. A U.S. drone strike in Somalia has targeted a key leader of the al-Shabab militant group who was involved in two attacks in Mogadishu more than a year ago that killed more than 30 people, at least three Americans among them, the Pentagon said Friday, April 1, 2016. Several U.S. officials said he and two others were killed. Hassan Ali Dhoore was targeted in the airstrike Thursday, but the U.S. military was still assessing the results, Pentagon spokesman Peter Cook said in a statement. (AP Photo/Mohamed Sheikh Nor, File)  (The Associated Press)

FILE - In this Thursday, Feb. 17, 2011 file photo, al-Shabab fighters march with their weapons during military exercises on the outskirts of Mogadishu, Somalia.  A U.S. drone strike in Somalia has targeted a key leader of the al-Shabab militant group who was involved in two attacks in Mogadishu more than a year ago that killed more than 30 people, at least three Americans among them, the Pentagon said Friday, April 1, 2016. Several U.S. officials said he and two others were killed. Hassan Ali Dhoore was targeted in the airstrike Thursday, but the U.S. military was still assessing the results, Pentagon spokesman Peter Cook said in a statement. (AP Photo/Mohamed Sheikh Nor, File)

FILE - In this Thursday, Feb. 17, 2011 file photo, al-Shabab fighters march with their weapons during military exercises on the outskirts of Mogadishu, Somalia. A U.S. drone strike in Somalia has targeted a key leader of the al-Shabab militant group who was involved in two attacks in Mogadishu more than a year ago that killed more than 30 people, at least three Americans among them, the Pentagon said Friday, April 1, 2016. Several U.S. officials said he and two others were killed. Hassan Ali Dhoore was targeted in the airstrike Thursday, but the U.S. military was still assessing the results, Pentagon spokesman Peter Cook said in a statement. (AP Photo/Mohamed Sheikh Nor, File)  (The Associated Press)

A U.S. drone strike in Somalia "most likely" killed Hassan Ali Dhoore, a senior leader of the terror group al-Shabab who had planned attacks that killed three Americans overseas, a U.S. official confirmed to Fox News Friday.

Dhoore was riding in a vehicle with two other al-Shabab members Thursday evening when the strike took place about 20 miles south of Jilib in southern Somalia, according to a senior U.S. defense official.

The Pentagon had been watching him off and on for a long time, the senior official adds, saying the Somali government was involved in sharing information that led to this strike.

U.S. officials say Dhoore helped facilitate a deadly Christmas Day 2014 attack at a Somali airport and a March 2015 attack at the Maka Al-Mukarramah Hotel, both in Mogadishu. U.S. citizens were among those killed in the two attacks, the officials said. 

In addition, investigators linked Dhoore to the assassination of a Somali parliament member who also had U.S. citizenship. Dhoore had continued to plot ways to target and kill Americans in the Somali capital, according to the Pentagon.

Dhoore's death, if confirmed, would mark a "significant blow" to the Al Qaeda-linked group and its ability to plan attacks, Pentagon Press Secretary Peter Cook said.

Despite being pushed out of Somalia's major cities and towns, al-Shabab continues to launch deadly guerrilla attacks across the Horn of Africa, and even across the border. The terror group was linked to a 2013 attack on the Westgate Mall in Kenya's capital of Nairobi in which 67 people were killed, as well as an April 2015 attack on Kenya's Garissa University, in which 148 people died.

Fox News' Jennifer Griffin, Lucas Tomlinson and The Associated Press contributed to this report.