The United States said Wednesday that it would increase security at overseas airports that have nonstop flights to the country. U.S. officials cited concerns that Al-Qaeda operatives in Syria and Yemen were developing bombs that could be smuggled onto planes.
The new security measures would be required at airports in Europe, Africa and the Middle East, the U.S. officials told Reuters on the condition of anonymity.
The Department of Homeland Security (DHS) said "enhanced security measures" would be implemented in the next few days at "certain overseas airports with direct flights into the United States."
It did not specify which airports or what countries would be affected, nor did it say what triggered the extra precautions.
"We are sharing recent and relevant information with our foreign allies and are consulting the aviation industry," DHS Secretary Jeh Johnson said in a release.
Johnson said he directed the Transportation Security Administration to implement the measures in the coming days. The move comes during the summer travel season and days before the July 4 holiday.
A U.S. official told Reuters that some of the new measures would involve additional inspections of passengers' shoes and property.
The official said Washington had legal authority to enforce new security requirements on foreign governments or airports because the flights go directly to the United States.
Earlier, law enforcement and security officials told Reuters the United States and European authorities were discussing measures that could include installation of additional bomb-detection machines.
Bomb makers from the Nusra Front, Al-Qaeda's affiliate in Syria, and Yemen-based Al-Qaeda in the Arabian Peninsula, or AQAP, are believed to be working together in an effort to develop explosives that could avoid detection by current airport screening systems, U.S. national security sources said.
The main concern is that militant groups could try to blow up U.S.- or Europe-bound planes by concealing bombs on foreign fighters carrying Western passports who spent time with Islamist rebel factions in the region, the sources said.
There was no immediate indication that U.S. intelligence had detected a specific plot or time frame for carrying out an attack.
Al Jazeera and Reuters