U.S. Navy SEALs are believed to have carried out a pre-dawn raid Saturday on a Somali coastal base housing members of the armed group Al-Shabab.
Military officials told a number of U.S. media outlets that the operation was aimed at “high-profile” targets of the group. It comes two weeks after members of Al-Shabab claimed responsibility for a four-day assault at the Westgate mall in Nairobi, in which at least 67 people were killed.
Al-Shabab said earlier on Saturday that a group of "Westerners" had arrived in boats under the cover of dark and attacked a house in one of its coastal bases.
U.S. officials later told the Reuters news agency that no Al-Shabab leaders had been taken into custody during the raid.
Al-Shabab had initially claimed that British and Turkish soldiers were involved in the attack and that a British soldier was killed. Both nations denied any involvement.
Al Jazeera's Peter Greste, reporting from Mogadishu, quoted Somali government and Western intelligence sources as saying that they believe U.S. forces were involved in the attack.
"We don't know whether there are any non-U.S. troops that might have been involved with this," Greste said.
Later on Saturday, The New York Times, citing an unnamed American security official, reported that a U.S. Navy SEAL team carried out the pre-dawn mission.
A Pentagon spokesperson confirmed late on Saturday that the U.S. military was involved in an operation, "against a known Al-Shabab terrorist," but declined to provide any further information.
Foreign forces landed on the beach at Barawe, about 110 miles south of Mogadishu, and launched an assault that drew gunfire from rebel fighters, Sheikh Abdiasis Abu Musab, spokesman for Al-Shabab's military operations, told Reuters.
"Westerners in boats attacked our base at Barawe beach and one was martyred from our side," Musab said.
"No planes or helicopters took part in the fight. The attackers left weapons, medicine and stains of blood, we chased them," he said.
"The sources say there were some very high-value targets, including the leader of Al-Shabab himself, known as Godane," Greste said. "We understand that, although the Western sources believe that one of the senior Al-Shabab commanders may have been killed, they do understand that Ahmed Godane may have survived."
Al-Shabab insists there was nobody of any significance in the house at the time of Saturday's attack, Greste said.
Many residents said they were woken by the attack late on Friday night.
"We were awoken by heavy gunfire last night, we thought an Al-Shabab base at the beach was captured," Sumira Nur, a mother of four, told Reuters from Barawe on Saturday.
"We also heard sounds of shells but we do not know where they landed. We don't have any other information," she said.
Although the United States does not report its activities in Somalia, it has used drones in recent years to kill Somali and foreign Al-Shabab fighters.
In January, the French military used helicopters to attack an Al-Shabab base in a southern Somalia village to rescue a French hostage. Two French commandos were killed in the assault.
Western nations are worried that Somalia will sink back into chaos and provide a launch pad for militancy despite a fragile recovery after two decades of war.
Al-Shabab was driven out of Mogadishu in late 2011 and is struggling to hold on to territory elsewhere in the face of attacks by Kenyan, Ethiopian and African Union forces trying to prevent the group from spreading outside of Somalia. Al-Shabab wants to impose its strict version of sharia, or Islamic law, across the Horn of Africa state.
Al Jazeera and wire services