The al Qaeda threat that closed U.S. embassies in the Middle East on Sunday is the most serious in years and the "chatter" among suspected terrorists is reminiscent of what preceded the September 11 attacks, a U.S. lawmaker who is briefed on intelligence said.
The State Department closed 21 embassies and consulates and issued a worldwide travel alert warning Americans that al Qaeda may be planning attacks in August, particularly in the Middle East and North Africa.
"There is an awful lot of chatter out there," Senator Saxby Chambliss, the top Republican on the Senate Intelligence Committee, said on NBC's "Meet the Press."
He said "chatter" - electronically monitored communications among terrorism suspects about the planning of a possible attack - was "very reminiscent of what we saw pre-9/11."
The threat also has prompted some European countries to close their embassies in Yemen, where an al Qaeda affiliate, al Qaeda in the Arabian Peninsula, is based.
"This is the most serious threat that I've seen in the last several years," Chambliss said.
A U.S. intelligence official told Reuters there was disagreement within the intelligence community over whether the potential target was in Yemen or more broadly in the region, which was why the State Department's alert described the threat as "possibly occurring in or emanating from the Arabian Peninsula."
The threat information also is coming ahead of the Eid celebration at the end of the Muslim holy month of Ramadan later this week and just over a month before the anniversary of al Qaeda's Sept. 11, 2001, attacks on the United States.
A September 11 attack last year killed the U.S. ambassador to Libya and three other Americans in Benghazi.
Chambliss said one of the surveillance programs revealed by former spy agency contractor Edward Snowden had helped gather intelligence about this threat.
Those programs "allow us to have the ability to gather this chatter," he said. "If we did not have these programs then we simply wouldn't be able to listen in on the bad guys."