The United States is warning Americans in Sudan that they could be targets for a group with potential links to al-Qaida.
Officials are also telling U.S. citizens to stay away from a popular cafe in the Sudanese capital of Khartoum.
They says the Ozone cafe, located in an affluent district, is especially vulnerable.
The U.S. embassy in Khartoum said Saturday the threat comes from a group calling itself "Al-Qaida in the Land of the Two Niles".
Officials say the group issued a statement referring to the murder of a U.S. aid official and his driver in January, and promised its jihad against "America and its allies of crusaders and apostates will continue."
Five Sudanese men have been charged with the fatal shooting in the New Year's Day attack. A previously unknown militant group called Ansar al-Tawhid claimed responsibility for the killings.
Sudan hosted al Qaida leader Osama bin Laden in the 1990s, and remains on the U.S. list of state sponsors of terrorism.
The U.S. embassy in Khartoum initially issued the warning about "Al-Qaida in the Land of the Two Niles" on its website on October 2nd.
Some information for this report provided by AFP and Reuters.