By Elias Biryabarema
KAMPALA (Reuters) - Ugandan authorities have uncovered a "terrorist cell" run by the Somali militant Islamist group al Shabaab, which they believe was planning an imminent attack, the U.S. Embassy in Uganda said on Saturday.
"At this point we are not aware of specific targets, and the Ugandan authorities have increased security at key sites, including Entebbe International Airport," the embassy said in a statement on its website.
Uganda, as one of the countries that contribute forces to an African Union peacekeeping mission battling al Shabaab in Somalia, has suffered militant attacks in recent years, and al Shabaab has threatened more.
The U.S. Embassy, shortly before issuing its announcement, told its citizens, in a message posted on Twitter, to stay at home or proceed to a safe location while Ugandan authorities completed operations against a suspected cell in Kampala.
Ugandan police declined comment but were due to hold a press conference shortly.
Al Shabaab, which is aligned with al Qaeda, claimed responsibility for the attack on the Westgate shopping mall in Nairobi in neighboring Kenya a year ago, in which 67 people died.
This month the group warned of revenge against its enemies after it said its leader Ahmed Godane had been killed in a U.S. air strike on his encampment in Somalia.
In 2010, Al Shabaab bombed sports bars in Uganda where people were watching the soccer World Cup on television.
The U.S. Embassy says Uganda faces a "continued threat" and has issued other alerts during the year about possible attacks.
(Writing by Edith Honan; Editing by Pravin Char and Susan Fenton)