The United States has issued a worldwide travel alert warning that al-Qaeda may be planning attacks in August in the Middle East and beyond.
In a statement, the US State Department said the potential for an attack was particularly strong in the Middle East and North Africa, the BBC reports.
The alert warned that al-Qaeda and affiliated organizations may focus efforts to conduct attacks in the period between now and the end of August, and said there was potential for terrorists to attack public transport systems and other tourist infrastructure.
The warning came shortly after the US announced 21 of its embassies and consulates would be shut on Sunday.
Britain also announced on Friday it was closing its embassy in Yemen for two days due to security concerns. The Foreign Office said the UK embassy in Yemen would shut on 4 and 5 August as a precautionary measure.
A spokesman would not say if the closure was in response to a specific threat. "We are particularly concerned about the security situation in the final days of Ramadan and into Eid," the spokesman said.
The US diplomatic missions closed on Sunday are in United Arab Emirates, Algeria, Jordan, Iraq, Egypt, Saudi Arabia, Djibouti, Bangladesh, Qatar, Afghanistan, Sudan, Kuwait, Bahrain, Oman, Mauritania, Yemen and Libya.