A terrorism threat has prompted the United States to close dozens of American diplomatic missions in the Middle East, North Africa and elsewhere through the weekend, American officials said Thursday.

Officials gave few details about what prompted the move to close an unusually large number of American missions, but said there was “credible” information that an Al Qaeda regional affiliate might be plotting an attack sometime in the coming days.

“It’s not often that we close a bunch of embassies at once,” said one official, adding that the threat was being taken particularly seriously by American intelligence agencies.

The official said that the State Department was planning to have nearly all American diplomatic facilities in the Middle East, North Africa and South Asia closed through the weekend, including missions in Egypt, Iraq, Israel, Kuwait and Saudi Arabia. In much of the Muslim world, diplomatic facilities are generally closed on Friday and Saturday, but open on Sunday.