The United States intercepted electronic communications this week among senior operatives of Al Qaeda, in which the terrorists discussed attacks against American interests in the Middle East and North Africa, American officials said Friday.
The intercepts and a subsequent analysis of them by American intelligence agencies prompted the United States to issue an unusual global travel alert to American citizens on Friday, warning of the potential for terrorist attacks by operatives of Al Qaeda and their associates beginning Sunday through the end of August. Intelligence officials said the threat focused on the Qaeda affiliate in Yemen, which has been tied to plots to blow up American-bound cargo and commercial flights.
The bulletin to travelers and expatriates, issued by the State Department, came less than a day after the department announced that it was closing nearly two dozen American diplomatic missions in the Middle East and North Africa, including facilities in Egypt, Iraq, Yemen, Kuwait and Saudi Arabia. Britain said Friday that it would close its embassy in Yemen on Monday and Tuesday because of “increased security concerns.”
It is unusual for the United States to come across discussions among senior Qaeda operatives about operational planning — through informants, intercepted e-mails or eavesdropping on cellphone calls. So when the high-level intercepts were collected and analyzed this week, senior officials at the C.I.A., State Department and White House immediately seized on their significance. Members of Congress have been provided classified briefings on the matter, officials said Friday.
“This was a lot more than the usual chatter,” said one senior American official who had been briefed on the information but would not provide details. Spokesmen for the State Department and the C.I.A. also declined to comment on the intercepts.
The importance of the intercepts was underscored by a speech that the Qaeda leader, Ayman al-Zawahri, posted on jihadist forums on Tuesday. In his address, Mr. Zawahri called for attacks on American interests in response to its military actions in the Muslim world and American drone strikes in Pakistan and Yemen, according to the SITE Intelligence Group, which monitors statements by jihadists.
Security analysts said Friday that in the aftermath of the furor over the Obama administration’s handling of the attack last year on the diplomatic mission in Benghazi, Libya, the State Department is now more likely to publicize threat warnings when deemed credible, both to alert the public and to help deter any imminent attacks.
“A decision to close this many embassies and issue a global travel warning for a month suggests the threat is real, advanced and imminent but the intelligence is incomplete on where,” said Bruce Riedel, a former C.I.A. case officer and a Brookings Institution scholar.
The embassy closings come toward the end of the Ramadan holidays and the approaching first anniversary of the terror attack Sept. 11 on the American diplomatic compound in Benghazi that killed four Americans, including Ambassador J. Christopher Stevens.
“We are particularly concerned about the security situation in the final days of Ramadan and into Eid,” the British Foreign Office said in a statement, referring to the Muslim holy month that ends Wednesday evening.
Obama administration officials publicly declined to discuss what specific information had prompted the increased alarm and alerts, citing a desire to protect classified sources and methods.
But intercepting electronic communications is one the National Security Agency’s main jobs, as the documents leaked by Edward J. Snowden, a former N.S.A. contractor, have only underscored. At the request of intelligence officials, The New York Times withheld some details about the intercepted communications.
Some analysts and Congressional officials suggested Friday that emphasizing a terrorist threat now was a good way to divert attention from the uproar over the N.S.A.’s data-collection programs, and that if it showed the intercepts had uncovered a possible plot, even better.
The bulletin by the State Department’s Bureau of Consular Affairs did not advise against travel to any particular country, but it warned Americans to be particularly mindful of their surroundings, especially in tourist areas, and recommended that they register their travel plans with the State Department.
“Terrorists may elect to use a variety of means and weapons and target both official and private interests,” the bulletin said. “U.S. citizens are reminded of the potential for terrorists to attack public transportation systems and other tourist infrastructure. Terrorists have targeted and attacked subway and rail systems, as well as aviation and maritime services.”
Representative Ed Royce, a California Republican and the chairman of the House Foreign Affairs Committee, said Friday that the warning was linked to a Qaeda threat focused on the Middle East and Central Asia.
To date, the only Qaeda affiliate that has shown a desire and ability to attack American facilities overseas is Al Qaeda in the Arabian Peninsula, a group based in Yemen.
The Qaeda affiliate announced in July that its second-in-command, Saeed al-Shihri, a former Guantánamo Bay prisoner, had died as a result of injuries sustained in an American missile strike in Yemen last year. But Ibrahim Hassan al-Asiri, the group’s seminal bomb maker, remains at large, and, according to American officials, has trained a cadre of skilled protégés ready to take his place should he be killed.
American drones over the past week have carried out three separate strikes in Yemen, according to Long War Journal, a Web site that tracks drone strikes. There have been 15 American drone strikes in Yemen this year, according to the site.
The State Department has issued similar alerts and warnings in the past, American officials said Friday. The last time the department issued a global travel alert was after the death of Osama bin Laden in May 2011.
On Feb. 19 this year, the State Department issued a “caution” notice — less severe than a “warning” or “alert” — to Americans that “current information suggests that Al Qaeda, its affiliated organizations and other terrorist organizations continue to plan terrorist attacks against U.S. interests in multiple regions.”
Pentagon officials said Friday that there had been no movements of troops or other forces in response to the embassy closings.
After the attack in Benghazi, the military’s Africa Command bolstered its quick-reaction forces in Djibouti and created new Marine Corps reaction forces in Morón, Spain, and at the naval air station in Sigonella in Italy that can respond to a crisis within a few hours.