The US embassy in Uganda warned on Thursday of a "specific threat" by an unknown group to attack the international airport serving the capital Kampala.
The alert came as travellers flying to the United States from Europe and the Middle East faced tighter security because of new concerns about the development of explosives that could circumvent airport security.
"The US embassy has received information from the Uganda police force that according to intelligence sources there is a specific threat to attack Entebbe International Airport by an unknown terrorist group today, July 3rd, between the hours of 21.00 - 23.00 (18.00 GMT to 20.00 GMT)," the statement said.
Although it did not name any group, al-Qaeda linked Shebab insurgents have claimed recent attacks in Kenya and Djibouti.
Uganda has troops in Somalia as part of the African Union force fighting the Shebab and is on high alert amid fears of attacks by the Islamist militants.
The US embassy said people planning travel through the airport during on Thursday evening may want to review their plans in light of the warning.
It also warned its citizens of a general threat of attacks which could target hotels, restaurants, clubs, malls, diplomatic missions, government buildings and transport.
The Shebab claimed responsibility for the assault on the Westgate shopping centre that killed at least 67 people in the Kenyan capital of Nairobi in September last year as well as for two nighttime attacks on the Kenyan coast last month that killed around 60 people.
In May, a male and female suicide bomber blew themselves up in an attack on restaurant popular with Westerners in central Djibouti, killing a Turkish national.