2 August 2013 Last updated at 16:20 GMT
The US state department has said it
is issuing a global travel alert because of an unspecified al-Qaeda threat.
In a statement, the department said the potential for an attack was
particularly strong in the Middle East and North Africa.
The move comes shortly after the US announced 21 embassies and consulates in
18 counties would be shut on Sunday.
The alert expires on 31 August 2013, the department said. It recommended US
citizens travelling abroad be vigilant.
"Current information suggests that al-Qa'ida and affiliated organizations
continue to plan terrorist attacks both in the region and beyond, and that they
may focus efforts to conduct attacks in the period between now and the end of
August," the statement said.
'Not chit chat'
Dutch Ruppersberger, the top Democrat on the House intelligence committee,
said the threat was not prompted by "the regular chit chat" gleaned from
would-be militants online or elsewhere.
"The most important thing we have to do is protect American lives," he told
the Associated Press news agency.
Four Americans died in an attack last year on the US
consulate in Benghazi, Libya
An unnamed senior US official
told
NBC the threat may be related to the Islamic holy month of Ramadan, which
ends next week.
In the Muslim world, Sunday is a work day. In other parts of the world US
diplomatic offices are shut on Sunday.
"It is possible we may have additional days of closing as well," a senior
state department official told the BBC on Thursday.
The official said the state department had "been apprised of information"
leading it to take these "precautionary steps... out of an abundance of
caution".
Last year on 11 September, the US consulate in Benghazi, Libya, was attacked,
leaving four Americans dead.
Other embassies are routinely targets of protesters.
The US diplomatic missions to be closed on Sunday are in Abu Dhabi, United
Arab Emirates; Algiers, Algeria; Amman, Jordan; Baghdad, Iraq; Cairo, Egypt;
Dhahran, Saudi Arabia; Djibouti, Djibouti; Dhaka, Bangladesh; Doha, Qatar;
Dubai, United Arab Emirates; Erbil, Iraq; Jeddah, Saudi Arabia; Kabul,
Afghanistan; Khartoum, Sudan; Kuwait City, Kuwait; Manama, Bahrain; Muscat,
Oman; Nouakchott, Mauritania; Riyadh, Saudi Arabia; Sanaa, Yemen and Tripoli,
Libya.
