KAMPALA: The US Embassy in Uganda warned on Thursday of a specific threat by an unknown terrorist group to attack the country’s only international airport.

The Entebbe International Airport could be attacked on Thursday between 9 p.m. and 11 p.m. local time, the embassy said on its website, citing information obtained from Ugandan police. The statement urged US citizens traveling through Entebbe around that time to “review their plans in light of this information.” Entebbe is 36 kilometers south of the capital, Kampala.

There is a “continued threat of potential terrorist attacks in the country,” with targets ranging from nightclubs to government offices, the statement said.

US intelligence officials are concerned that Al-Qaeda is trying to develop a new and improved bomb that could go undetected through airport security.

There is no indication that such a bomb has been created or that there’s a specific threat to the US, but the Obama administration on Wednesday called for tighter security measures at foreign airports that have direct flights to the US American intelligence has picked up indications that bomb makers from Yemen-based Al-Qaeda in the Arabian Peninsula have traveled to Syria to link up with the Al-Qaeda affiliate there, known as the Nusra Front, according to a counterterrorism official who spoke on condition of anonymity because he was not authorized to speak publicly about the matter by name. The enhanced security measures have been in the works for the past month, he said.

British airports stepped up security after the reports.

Al-Qaeda in the Arabian Peninsula long has been fixated on bringing down airplanes with hidden explosives. It was behind failed and thwarted plots involving suicide bombers with explosives designed to be hidden inside underwear and explosives secreted inside printer cartridges shipped on cargo planes.

Over the past year, Americans and others from the West have traveled to Syria to join the fight against the Syrian government. The fear is that fighters with a US or other Western passport, who therefore are subject to less stringent security screening, could carry such a bomb onto an American plane.

The counterterrorism official declined to describe the bomb. But officials in the past have raised concerns about non-metallic explosives being surgically implanted inside a traveler’s body, designed to be undetectable in pat-downs or metal detectors.

The call for increased security was not connected to Iraq or the recent violence there, said a second US counterterrorism official who was not authorized to speak publicly by name.