A US Air Force AC-130 gunship has launched a second air strike against suspected Al-Qaeda operatives in southern Somalia, the Washington Post reported on Wednesday, citing unidentified US officials.
No confirmation of Monday's reported attack was immediately available in the region and a Pentagon spokesman declined to comment.
The newspaper said there was no information on the results or the specific targets of the strike.
An AC-130 gunship two weeks ago attacked what Washington said were Al-Qaeda agents fleeing with Islamist forces defeated by Somali government and Ethiopian troops late last month.
It was the first overt US action in Somalia since the end of a disastrous peacekeeping mission in 1994.
Somali government spokesman Abdirahman Dinari said he was not aware of a second US attack.
Washington believes Somali Islamists harbored Al-Qaeda members accused of bombing two U.S. embassies and an Israeli-owned hotel in east Africa.
Any prolonged US intervention in Somalia would be sure to inflame political passions there, joining the chorus of Muslims who see the "war on terror" as a crusade against Islam.
A freelance Somali journalist said on Sunday he had seen US troops on the ground in south Somalia working with Ethiopian forces hunting fugitive Islamists. Ethiopia vehemently denied the report.
Rumors have swirled for days that US personnel were inside Somalia since the January 8 strike but there has been no official confirmation of a US ground presence.
Mortars were fired at Mogadishu airport on Wednesday, killing one person and injuring another after a UN delegation arrived in the Somali capital, a government source said.
"A UN delegation just arrived and as soon as they left the plane, two mortar shells hit the airport," the source said.
"One person was killed while another was injured," the source said, adding the victims were Somalis. The UN Development Programme delegation was taken to an agency compound.
A spate of attacks, mainly against Ethiopian troops backing Somalia's interim government, have rocked the capital since they helped oust Islamists from Mogadishu and much of the south they had controlled for six months in a lightning December offensive.
The Islamists and some foreign supporters have vowed to wage guerrilla war against Ethiopian troops in the country, and many Somalis suspect their militants have been behind the attacks.
Ethiopian Prime Minister Meles Zenawi said on Wednesday some 200 soldiers had withdrawn from the chaotic nation
"We have organised that the last phase of withdrawal will coincide with deployment of AU forces," Meles told a news conference in Addis Ababa. "There will be no vacuum."
The African Union (AU) has approved a nearly 8,000-strong peacekeeping force for Somalia, but experts doubt its capacity to muster it, let alone tame a nation in anarchy since the 1991 ouster of dictator Mohamed Siad Barre.
The Islamists have been pushed into the remote southern tip near Kenya's border and Nairobi has in custody top Islamist leader Sheikh Sharif Ahmed.
A Kenyan government official said on Wednesday Ahmed would not be deported to Somalia because he would be killed and that he has asked for refuge in Yemen.