|Somali group says base raided by 'Westerners'|
Sources say US forces may have been involved in sea-borne assault at Barawe that killed at least one al-Shabab fighter.
Al-Shabab says it carried out the recent attack on a Nairobi shopping mall that killed at least 67 people [AP]
The Somali armed group al-Shabab has said that a group of "Westerners" who arrived in boats attacked a house in one of its coastal bases under the cover of night, drawing gunfire from rebels and killing one.
Foreign forces landed on the beach at Barawe, about 180km south of the capital Mogadishu, and launched an assault that al-Shabab attempted to repel, Sheikh Abdiasis Abu Musab, spokesman for the group's military operations, told Reuters news agency.
"Westerners in boats attacked our base at Barawe beach and one was martyred from our side," he said.
"No planes or helicopters took part in the fight. The attackers left weapons, medicine and stains of blood. We chased them."
It was not immediately clear whether the assault was related to the attack on a Kenyan shopping mall two weeks ago, claimed by al-Shabab, in which 67 people were killed by attackers using machine guns and grenades.
Al Jazeera's Peter Greste, reporting from Mogadishu, quoted Somali government and Western intelligence sources as saying that they believe US forces were involved in the attack.
"We don't know whether there are any non-US troops that might have been involved with this," he said.
He reported citing security sources that special forces troops targeted a safe house where many senior al-Shabab members, including leader Ahmed Abdi Goadane, were believed to be staying.
"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," our correspondent said.
Al-Shabab has denied Godane was there, but has acknowledged that one of its members was killed in the attack.
A resident of Barawe town told the Associated Press news agency that heavy gunfire woke people up before dawn prayers.
A similar account was given by a government official in Mogadishu who insisted on anonymity.
Somalia faces uphill struggle with al-Shabab fighters
"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 news agency from Barawe.
"We also heard sounds of shells but we do not know where they landed."
An al-Shabab member, who gave his name as Abu Mohamed, said fighters rushed to the scene to try to capture a foreign soldier but that they were not successful.
Western navies are patrolling the waters off the Horn of Africa nation - mired in conflict for more than two decades - and have in the past launched strikes on the shore from warships.
"This does not seem to be part of a widespread offensive, any kind of increase in the tempo of military operations against al-Shabab," Al Jazeera's Greste said.
"The main group who is responsible for dealing with al-Shabab here is the African Union peacekeeping mission, AMISOM."
In September 2009, a daylight commando raid carried out by a US Navy SEALS contingent in Barawe killed six people, including Saleh Ali Saleh Nabhan, a prominent al-Qaeda member in the region and an alleged plotter in the 1998 bombings at US embassies in Kenya and Tanzania that killed more than 250 people.
Al Jazeera and agencies