Fresh intelligence led the United States to conclude that operatives of al Qaeda in the Arabian Peninsula were in the final stages of planning an attack against U.S. and Western targets, several U.S. officials told CNN.
The warning led the U.S. State Department to issue a global travel alert Friday, warning al Qaeda may launch attacks in the Middle East, North Africa and beyond in coming weeks. The U.S. government also was preparing to close 22 embassies and consulates in the region Sunday as a precaution.
The chatter among al Qaeda in the Arabian Peninsula operatives had gone on for weeks but increased in the last few days, the officials said.
Taken together with a warning from Yemeni officials, the United States took the extraordinary step of shutting down embassies and issuing travel warnings, said the officials, who spoke on condition of anonymity.
While the specific target is uncertain, U.S. officials are deeply worried about a possible attack against the U.S. Embassy in Yemen occurring through Tuesday, the officials said.
The warnings also come as news has surfaced that al Qaeda's leader, Ayman al-Zawahiri, has appointed the head of al Qaeda in the Arabian Peninsula, Nasser al-Wahishi, as his overall general manager of the terror network, Seth Jones of the Rand Corporation said.
With al-Zawahiri, the man who succeeded Osama bin Laden, and al-Wahishi linked, the United States may be taking a cautious but necessary approach by closing the embassies, Jones said.
But as with so much in the intelligence world, there is disagreement over what may really be happening.
Officials have told CNN that some analysts believe the threat is solely in Yemen, while others are convinced plots are under way in several countries.
Even so, security has been greatly tightened across Yemen as a result of local intelligence that al Qaeda in the Arabian Peninsula was planning attacks in major cities, such as the capital, Sanaa, or Aden, a senior Yemeni national security official told CNN Friday.
Yemeni intelligence agencies alerted authorities of the threat two days ago, when the Yemeni president was in Washington, said the official, who spoke on condition of anonymity.
Britain, France and Germany said their embassies in Sanaa would also be closed on Sunday and Monday over security concerns.
The UK Foreign Office warned its citizens Friday against all travel to Yemen, and it strongly urged British nationals to leave now. "If you don't leave the country now while commercial carriers are still flying it is extremely unlikely that the British government will be able to evacuate you or provide consular assistance," according to the Foreign Office warning.
The steps showed heightened security concerns about intelligence that indicates a potential attack in Yemen.
According to three sources, the United States has information al Qaeda in Yemen was in the final stages of planning for an unspecified attack.
"The threat appears much worse than it has in a long time," the Yemeni official said.
Yemen has tightened security across the country, deploying security forces at all major government institutions, foreign embassies, foreign residential compounds and international organizations, the official said.
According to the Yemeni official, recent U.S. drone attacks may generate reprisals.
"We take these threats seriously, especially since al Qaeda has been dealt many blows over the last few days," the official said.
In 2011, al Qaeda in the Arabian Peninsula operatives filmed buildings linked to U.S. personnel in Sanaa, according to a source who has seen the video.
While the incident is not related to this week's terror warnings, it shows al Qaeda in the Arabian Peninsula's capabilities, CNN terrorism analyst Paul Cruickshank said.
Al Qaeda in the Arabian Peninsula operatives filmed video of the building, which is near the U.S. embassy in Sanaa, and the U.S. personnel who were in it, the source told Cruickshank.