WASHINGTON (AP/WJLA) -- Quickly and quietly in the middle of the night, the US military began loading Americans onto Air Force C-17 to get them out of Yemen as fast as possible.
Almost all of the employees of the US embassy there are now gone. American officials say that the terror plot they discovered in secret communications last week reaches the highest levels of Al-Qaeda.
According to one senior official, it was Ayman Al-Zaqahiri in Pakistan who directed the head of Al-Qaeda in Yemen to carry out a "big attack" with "strategic significance."
Yemen's Nasir Al Wuhayshi is also believed to be a participant -- he is one of the known terrorists behind the underwear bomb, printer cartridge bombs, and surgically-implanted explosives - small bombs that can be hidden inside the human body.
"This group is fairly ingenious, fairly bold, and eager to cause damage," says Coordinator for Counterterrorism Daniel Benjamin with the State Department.
When the US intercepted communication between the two men, the State Department moved quickly to close down American embassies throughout the Middle East, Africa, and South Asia.
Intelligence officials believe trucks have been packed with explosives to carry out the attack in Yemen - and now a frantic search is underway.
"Yemen is of course a country that doesn't have a very strong central government, and there's been lots of territory for the group to operate in and to use as a safe haven," says Benjamin.
The US ambassador is already back here in Washington, and it is unlikely that he will return to the Middle Easy anytime soon.
Yemeni security officials said a suspected U.S. drone strike at about 2 a.m. local time Tuesday killed four alleged al-Qaida members in a volatile eastern province of the country. The drone fired a missile at a car carrying the four men, setting it on fire and killing all of them, the officials said. It wasn't immediately clear if the decision to evacuate the embassy, made earlier, was connected to the drone strike.
The Yemeni officials, speaking on condition of anonymity because they are not allowed to talk to the media, said they believe one of the dead is Saleh Jouti, a senior al-Qaida member. It's the fourth drone attack in the past two weeks to hit a car believed to be carrying al-Qaida members.
Pentagon Press Secretary George Little said the U.S. Air Force transported State Department personnel out of Sanaa early Tuesday. "The U.S. Department of Defense continues to have personnel on the ground in Yemen to support the U.S. State Department and monitor the security situation," Little added.
Pentagon spokeswoman Eileen Lainez declined to provide additional details such as the number of people evacuated or the type of U.S. aircraft used.
Britain's Foreign Office also announced that it had evacuated all staff from its embassy in Yemen due to security concerns. The office said the British embassy staff were "temporarily withdrawn to the U.K." on Tuesday, but declined further comment. Previously, the U.K. had said the embassy would be closed until the end of the Muslim festival of Eid later this week.
A U.S. intelligence official and a Mideast diplomat told The Associated Press that the current shutdown of embassies in the Middle East and Africa was instigated by an intercepted secret message between al-Qaida chief Ayman al-Zawahri and Nasser al-Wahishi, the leader of the Yemen-based al-Qaida in the Arabian Peninsula, about plans for a major terror attack. The officials spoke on condition of anonymity because they were not authorized to discuss the matter publicly.
The State Department on Sunday closed a total of 19 diplomatic posts until next Saturday. They include posts in Bangladesh and across North Africa and the Middle East as well as East Africa, including Madagascar, Burundi, Rwanda and Mauritius.
Jen Psaki, spokeswoman for the State Department, said in a separate statement issued early Tuesday that the department issued the order for Yemen because of concern about a "threat stream indicating the potential for terrorist attacks against U.S. persons or facilities overseas, especially emanating from the Arabian Peninsula."
The statement said U.S. citizens who choose to stay in Yemen despite the travel warning should limit nonessential travel within the country and make their own contingency emergency plans.
AQAP, gathered in small cells scattered across Yemen's vast under-governed regions, has proven to be a tenacious enemy.
Officials say al-Zawahri, who took over for Osama bin Laden and works from Pakistan, has reached out to the Yemeni branch, cementing their ties and further signaling the AQAP is once again looking to target U.S. and Western interests after a sustained period of more local and regional focus.
For puzzled Americans who've been told that al-Qaida is on the decline, the latest warnings raise questions about how successful America's war on terror has been and whether the terror group has been able to reorganize and reconstitute itself since bin Laden's death in May 2011.
And, although U.S. officials agreed a year ago to restart military aid to Yemen, it's unclear how much of the new aircraft and weapons have arrived. After aid to Yemen was frozen for some time, the U.S. military is once again on the ground there training Yemeni special operations forces and has delivered more than a dozen helicopters to the Yemeni military and provided training for them, U.S. defense officials said.
But other weapons and equipment are still in the pipeline, according to a Mideast official.
The latest terror alert was triggered in part when the secret message between al-Zawahri and al-Wahishi was intercepted several weeks ago.
There long has been movement of fighters between Pakistan and Yemen, and discussions between the two groups, but the latest communication triggered worries and prompted the U.S. to take steps to boost security. The embassy closures came one day after a meeting between President Barack Obama and Yemeni President Abdo Rabu Mansour Hadi.
AQAP has been widely considered al-Qaida's most dangerous affiliate for several years. Even though the group lost Anwar al-Awlaki - one of its key inspirational leaders - to a U.S. drone strike in 2011, al-Wahishi and the group's master bomb maker, Ibrahim Hassan al-Asiri, remain on the loose and determined to target the U.S. and other Western interests.
The group is linked to the botched Christmas Day 2009 bombing of an airliner bound for Detroit and explosives-laden parcels intercepted aboard cargo flights a year later - both incidents involving al-Asiri's expertise.
In recent years, however, AQAP has been focused more on making gains at home, taking advantage of an unstable government and overstretched military that was forced to concentrate on protecting the political center in Sanaa. As a result, said a senior defense official, AQAP was able to expand its foothold in the south, capture more weapons and gain control of additional territory.