WASHINGTON — The United States has sharply increased attacks against Qaeda-backed Shabab militants in Somalia in recent days, conducting a flurry of airstrikes in the wake of the country’s deadliest terrorist assault last month and President Trump’s approval of new military authorities to hunt down insurgents around the world.
In a five-day stretch beginning Nov. 9, American drones and warplanes carried out six strikes against Shabab fighters outside Mogadishu, the Somali capital, and one strike against Islamic State combatants — one-quarter of the 28 strikes in the country this year. Last year, the military’s Africa Command said it conducted a total of 15 strikes in Somalia.
The strikes by armed American drones, which Pentagon officials said killed more than 40 fighters, came a month after a double truck bombing in Mogadishu left more than 380 people dead, and more than 300 others injured.
While no group has claimed the truck attacks, analysts suspect the Shabab, Somali-based militants who have terrorized the country and East Africa for years but who in recent years have lost much of their territory. The setbacks have been the result of attacks by African Union forces, a fitfully improving Somali Army and increasing American air power.
The Trump administration has redoubled its campaign to defeat the Shabab, but the group has proved to be a potent and resilient killing force.
As a result, the Pentagon in the past year has doubled the number of troops in Somalia to about 500, many of which are Special Operations forces dispatched to train and advise Somali army and counterterrorism troops, and conduct clandestine kill-or-capture raids of their own.
It is the largest American military presence in the Horn of Africa nation since the Black Hawk Down battle in 1993, when 18 Army soldiers died.
The military’s secretive Joint Special Operations Command has been particularly effective in building informant networks that lead to strikes. In turn, cellphones, laptop computers and documents captured after strikes generate information for additional attacks.
Mr. Trump gave the military wider latitude this year to go after militants in Somalia, specifically those associated with the Shabab. The head of the Africa Command, Gen. Thomas D. Waldhauser, waited months before exercising the authorities, citing the difficulty of striking militants who are mixed with a civilian population that is on the move in the midst of a regional famine.
“What’s going on now reflects the Trump administration’s desire to dial up the U.S. military effort, which has been increasing quietly for several months, combined with Shabab’s apparent intent to fight back as hard as it can,” said Michael R. Shurkin, a senior political scientist at the RAND Corporation and former C.I.A. analyst. “I just pray we’re bombing the right people.”
Africa Command officials have investigated a handful of reports of civilian casualties in Somalia, but insist that the vast majority of strikes have targeted only insurgents.
The deadly attack in Mogadishu last month spurred more aggressive strikes by the United States, which is working closely with Somali and other African forces on the ground, security analysts said.
Tricia Bacon, a Somalia specialist at American University in Washington and a former State Department counterterrorism analyst, said the increase in strikes was probably the result of “better and more actionable intelligence,” meaning fresh tips about insurgents that commandos can act on immediately.
Pentagon officials sought last week to play down any notion of a major American troop buildup or escalating operations in Somalia. They said it was more of a coincidence earlier this month that multiple painstaking efforts to identify, track and kill specific Shabab militants — without hurting civilians — all came together within a few days.
“There’s no particular rhythm to it, except that as they become available and as we’re able to process them and vet them, we strike them,” Lt. Gen. Kenneth F. McKenzie Jr., the director of the military’s Joint Staff, told reporters last week.
General McKenzie acknowledged that initial strikes can cause surviving militants to flee, making them more vulnerable to attack and creating a kind of chain reaction. “A strike produces movement, and other targets become available,” he said.
Samantha Reho, a spokeswoman for the Africa Command in Stuttgart, Germany, said, “We’ve always stressed the importance of putting pressure on the network.”
The intensifying operations have carried risks for American forces. In May, a Navy SEAL commando carrying out a raid with Somali troops was killed in an attack against Shabab fighters.
Shabab militants are not the only extremists the United States is now striking in Somalia. The American military bombed Islamic State fighters in northern Somalia for the first time on Nov. 3, and again on Nov. 12, a sign that the air campaign against the group was expanding after recent battlefield successes against the insurgents in Iraq and Syria.
A militant faction loyal to the Islamic State has increased its ranks in northern Somalia to as many as 200 fighters this year from a few dozen last year, according to a United Nations report issued this month. The increased militancy in the north has raised concerns among analysts that it could offer sanctuary for Islamic State militants fleeing defeat in Iraq or Syria.
The increasing number of American airstrikes in Somalia has prompted some analysts, as well as Somalis, to voice concerns over the risks of civilian casualties, which could feed into the Shabab’s anti-Western propaganda.
“Should civilian casualties happen, it’s to the advantage of the Shabab,” said Abdirahman Hassan Omar, a lawyer based in Mogadishu.
In recent weeks, the American military’s presence across Africa has come under rigorous scrutiny. A team of Green Berets and support soldiers was ambushed, along with more than two dozen Nigerien troops, on Oct. 4 near the border of Niger and Mali by militants believed to be associated with the Islamic State. Four American soldiers were killed.
In June, a Special Forces soldier, Staff Sgt. Logan J. Melgar, was found dead in his room in Bamako, Mali. It is unclear exactly how he died, but naval authorities are investigating whether two commandos from the Navy’s elite SEAL Team 6 strangled him.