US authorities plan to bolster security at some airports in Europe and the Middle East with direct flights to the United States, officials said.
Amid concern terror groups are developing new explosives to circumvent airport security, US Homeland Security Secretary Jeh Johnson announced unspecified steps that would be carried out in "the coming days," without saying which airports would be affected.
"We are sharing recent and relevant information with our foreign allies and are consulting the aviation industry," Johnson said in a statement.
After an assessment of security threats, Johnson said he had directed the Transportation Security Administration "to implement enhanced security measures in the coming days at certain overseas airports with direct flights to the United States."
Johnson said that "we will continue to adjust security measures to promote aviation security without unnecessary disruptions to the traveling public."
The airports were located in the Middle East and Europe, according to an official at the Department of Homeland Security, who spoke on condition of anonymity.
The announcement came before the country's Independence Day celebrations on Friday but officials would not say whether authorities had uncovered a specific threat or plot.
"There will be enhanced security measures in certain airports that fly non stop to the US," the DHS official told AFP.
"We're targeting certain airports abroad . . based on real time intelligence," the official added.
The new measures would be designed in a way to avoid creating major hassles for travelers, without signaling to potential terrorists what those steps would be, officials said.
"Information about specific enhancements is sensitive as we do not wish to divulge information about specific layers of security to those who would do harm," said a second DHS official, who asked not to be named.
The official said authorities "may require some additional screening of persons and their property, so travelers should always arrive at an airport with plenty of time for screening to be sure they do not miss their flights."
Media reports said the additional screening could apply to shoes worn by passengers and electronic devices.
US counter-terrorism experts in recent months have said there is cause for concern that extremists have come up with new tactics to avoid detection at airports.