The U.S. Embassy in Kampala, Uganda's capital, said Tuesday it was assessing "reports that a Westgate-style attack may soon occur" in the city.
Al-Shabaab, a terrorist group based in Somalia that has ties to al-Qaida, laid siege to the upscale Westgate shopping center in Nairobi, Kenya, in September. The attack left more than 60 people dead.
The embassy said it was sharing the information it had with Uganda authorities but had nothing specific about the attack.
U.S. State Department spokeswoman Jen Psaki said during her regular press briefing Thursday she wasn't going to get into specifics about the threat.
"We put out the [embassy] statement because of our concern and because of information available, but in terms of the specificity of that, I'm not going to outline that," she said.
U.S. Rep. Ed Royce, R-Calif., chairman of the House Foreign Affairs Committee, said in an Oct. 3 hearing he was concerned about al-Shabaab's threat to U.S. national security interests.
"While al-Shabaab has been primarily focused on attacking the young Somali government and African peacekeepers working to secure that country, this is changing," he said.
The U.S. State Department has not issued formal travel advisory for Uganda despite the embassy warning.