Barack Obama, the US president, has issued an executive order to freeze assets of individuals with ties to Somalia's al-Qaeda-linked al-Shabab movement.
Obama's directive allows the US treasury department to sanction or freeze the assets of individuals with suspected links to the piracy off Somalia's coast or those who have in any way been involved in threatening Somalia's stability.
The piracy and eroding security in Somalia "constitute an unusual and extraordinary threat to the national security and foreign policy of the United States," Obama said in his executive order on Tuesday.
The decree specifically targets anyone who threatens the peace, interferes with the delivery of humanitarian assistance or violates the United Nations arms embargo in the lawless nation.
Sheikh Hassan Dahir Aweys, a prominent Somali opposition figure, is one of those targeted by the new sanctions.
Last year Aweys said he was working to unite his Islamic Party with al-Shabab.
Al-Shabab is battling to overthrow the US-backed Somali government. Somalia has not had an effective government for about two decades.
US authorities say they are increasingly concerned that Somalia has become a safe haven for Islamic extremists and a sanctuary for al-Qaeda-linked training camps.
Meanwhile, al-Shabab fighters are claiming to have gained full control of the city of Baidoa in southern Somalia, which they have declared to be an Islamist province.
According to reports, the group's fighters last week disarmed guards at a UN World Food Programmes (WFP) base in Wajid, near Baidoa, and also seized control of the nearby airstrip.
The WFP, however, said that its base was empty and the move would not affect its operations.