NEW YORK (CBSNewYork/AP) – Following what some called the most credible terrorist threat since Sept. 11, 2001, nearly two dozen U.S. embassies and consulates abroad were closed Sunday.

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Travelers headed abroad are also on high alert as a result of the terror warning.

As CBS News’ Marlie Hall reported, barriers and extra security surrounded many of the 22 American embassies and consulates across the Muslim world Sunday, Members of Congress said intelligence agencies intercepted conversations between high-level people from al Qaeda in the Arabian Peninsula about a major terrorist attack.

Click here for list of embassies closed on Sunday

There has been an awful lot of chatter out there. Chatter means conversations among terrorists about the planning that is going on — very reminiscent of what we saw pre 9-11,” said U.S. Sen. Saxby Chambliss (R-Ga.)

The U.S. State Department said shut down on Sunday may remain closed for days.
Helicopters conducted surveillance over the U.S. Embassy in Afghanistan this weekend, and police searched people at a checkpoint nearby.

There were also roadblocks Sunday leading to the U.S. embassy in Yemen, which is home to the al-Qaida in the Arabian Peninsula — the al Qaeda affiliate charged with attacking Americans.

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“I think we know a lot more about the when, not the where, and you can tell that from the breadth of the closures,” said U.S. Rep. Adam Schiff (D-Calif.) “The when was very specific in terms of a Sunday.”

Rep. Peter King, a New York Republican who chairs a panel on counterterrorism and intelligence, also said the threat included dates but not locations of possible attacks.

“The threat was specific as to how enormous it was going to be and also that certain dates were given,” King said. He added that while authorities assume any attack is likely to come in the Middle East, warnings to state and local authorities in the U.S. were warranted because of the uncertainty.

“This is a wake-up call,” King said. “Al Qaeda is in many ways stronger than it was before 9/11 because it has mutated and it’s spread in dramatically different locations. And al Qaeda in the Arabian Peninsula is the most deadly of all the al Qaeda affiliates.”

U.S. authorities are concerned about a potential repeat of last year’s riots and attacks on several embassies, including the deadly assault in Benghazi, Libya that killed four Americans.

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CBS News has learned a team of terrorists is already in place to carry out a new attack. U.S. agencies are rushing to disrupt the plot.

“This is probably one of the most specific and credible threats that I’ve seen probably since 9-11, and that is why everyone is taking this so seriously,” said Rep. Michael McCaul (R-Texas.) “In fact, the Chairman of the Joint Chiefs of Staff called it extremely significant.”

As CBS 2’s Janelle Burrell reported from John F. Kennedy International Airport on Sunday, some air travelers were taking the global travel advisory warnings in stride.

“Everyone’s just like, ‘be careful,'” Gehad Saber, who is traveling to Egypt with her father, told Burrell. “I feel scared sort of but I still have hope that everything will stay safe.”

Americans traveling to the targeted regions have been urged to take serious caution as a result.

“If you have to travel, if you’re already there, try to stay away from any American-owned or American organizations,” security expert Manny Gomez told Burrell.

The travel alert is set to expire at the end of the month.

Travelers headed to the regions under the travel advisory are encouraged to register their itinerary with an embassy, Burrell reported.

On Friday the Obama administration announced the weekend closures and the State Department announced a global travel alert.

The warning urged American travelers to take extra precautions overseas, citing potential dangers involved with public transportation systems and other prime sites for tourists. It noted that previous terrorist attacks have centered on subway and rail networks as well as airplanes and boats. It suggested travelers sign up for State Department alerts and register with U.S. consulates in the countries they visit. The alert expires on Aug. 31.

The statement said that al Qaeda or its allies might target either U.S. government or private American interests.

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