US missions across the Middle East and Africa will be closed through August 10, officials said Sunday, amid intelligence reports an al Qaeda attack may be imminent. The state department, noting it was acting "out of an abundance of caution," said 19 diplomatic outposts would be shuttered through Saturday. The list includes 15 that were already ordered closed Sunday due to the security fears, as well as four additional posts. "This is not an indication of a new threat stream, merely an indication of our commitment to exercise caution and take appropriate steps to protect our employees, including local employees and visitors to our facilities," state department spokeswoman Jen Psaki said in a statement.At least 25 US embassies and consular offices had initially been ordered closed Sunday in response to a terror threat, a move lawmakers said was prompted by intercepts of high-ranking al Qaeda operatives signaling a major attack.Briefed members of Congress called the intelligence reporting among the most serious they have seen in recent years.The chairman of the House Homeland Security Committee, Michael McCaul called it "probably one of the most specific and credible threats I've seen, perhaps, since 9/11."He said an attack appeared to be "imminent," possibly timed to coincide with the last night of Ramzan, the Muslim holy month.Representative Dutch Ruppersberger, the top Democrat on the House Intelligence Committee, told ABC's "This Week" that al Qaeda's "operatives are in place."He said the United States knows this "because we've received information that high level people from al Qaeda in the Arabian Peninsula are talking about a major attack."General Martin Dempsey, chairman of the Joint Chiefs of Staff, told ABC News the threats were "more specific" than previous threats.While an exact target was unknown, "the intent seems clear. The intent is to attack Western, not just US, interests," Dempsey said.ABC News cited an unnamed US official as saying there was concern that al Qaeda might deploy suicide attackers with surgically implanted bombs to evade security.The diplomatic posts to be closed through Saturday included those in: Abu Dhabi, Amman, Cairo, Riyadh, Dhahran, Jeddah, Doha, Dubai, Kuwait, Manama, Muscat, Sanaa, Tripoli, Antananarivo, Bujumbura, Djibouti, Khartoum, Kigali, and Port Louis.The new closures are located in Madagascar, Burundi, Rwanda and Mauritius. The outposts that are reopening include those in Afghanistan, Algeria, Bangladesh, Mauritania, Iraq, and Israel.Security was especially tight in Yemen's capital Sanaa on Sunday where Britain, France and Germany also shuttered their embassies in the wake of the US warning late last week. Special forces with armored personnel carriers were stationed outside the buildings as police and army checkpoints went up on all the city's main thoroughfares.Residents said they heard the sound of a drone overhead, which could only be American as Washington is the sole power to operate the unmanned aircraft in the region. The United States considers al Qaeda in the Arabian Peninsula to be the jihadist network's most active and dangerous branch, and has waged an intensifying drone war against AQAP militants in Yemen.In Jordan, meanwhile, authorities beefed up security around the closed US mission."Authorities have conducted a sweep for explosives at all US diplomatic locations and beefed up security measures around the US embassy," a Jordanian security official told AFP.Although Washington has responded to terrorist threats before by closing diplomatic missions, this was believed to be the most widespread closure ever."I've spent 21 years in the CIA, and I don't think I've ever seen 22 embassies closed simultaneously. This is very, very unusual," Robert Baer, a former US case officer in the Middle East, told CNN.Baer said the US action comes amid an Al-Qaeda resurgence, including prison breaks in Libya and Iraq in which hundreds of inmates have escaped, and turmoil in Egypt, Mali and elsewhere in the region.Adding further tension to the situation, Interpol on Saturday issued a security alert after hundreds of militants were freed in jailbreaks.The worldwide police agency said it suspected al Qaeda was involved in the getaways across nine countries, notably Iraq, Libya and Pakistan, that had "led to the escape of hundreds of terrorists and other criminals" in the past month alone.The state department late last week issued a worldwide travel alert to US citizens, warning of the "potential for terrorists to attack public transportation systems and other tourist infrastructure."Hours after the US alert was issued, an audio recording was posted on militant Islamist forums in which al Qaeda chief Ayman al-Zawahiri accused the United States of "plotting" with Egypt's military, secularists and Christians to overthrow Islamist president Mohamed Morsi.Washington has been especially cautious about security abroad since an attack on its consulate in the Libyan city of Benghazi on September 11 last year.Ambassador Chris Stevens and three other Americans were killed in the attack blamed on Islamist militants.