The US says it will keep a number of embassies in north Africa and the Middle East closed until Saturday, due to a possible militant threat.
Twenty-one US embassies and consulates closed on Sunday.
The State Department in Washington said the extended closures were "out of an abundance of caution", and not a reaction to a new threat.
Britain said its embassy in Yemen would stay closed until the end of the Muslim festival of Eid on Thursday.
The UK Foreign Office had earlier announced it would shut its mission in the Yemeni capital Sanaa until Tuesday.
Meanwhile US diplomat missions in Algiers, Kabul and Baghdad are among those which will reopen on Monday, Washington said.
But its diplomatic posts in Abu Dhabi, Amman, Cairo, Riyadh, Dhahran, Jeddah, Doha, Dubai, Kuwait, Manama, Muscat, Sanaa and Tripoli will remain closed until Saturday.
The US state department also added African missions in Antananarivo, Bujumbura, Djibouti, Khartoum, Kigali and Port Louis to the list, meaning a total of 19 US embassies will be closed this week.
A state department global travel alert, issued on Friday, is in force until the end of August.
The department said the potential for an al-Qaeda inspired attack was particularly strong in the Middle East and North Africa.
Embassies closed on Sunday, a working day in the Muslim world, included Amman, Cairo, Riyadh and Dhaka.
The embassy closures and US global travel alert came after the US reportedly intercepted al-Qaeda messages.
It has been suggested that they were between senior figures talking about a plot against an embassy.
Twenty-one US embassies and consulates closed on Sunday.
The State Department in Washington said the extended closures were "out of an abundance of caution", and not a reaction to a new threat.
Britain said its embassy in Yemen would stay closed until the end of the Muslim festival of Eid on Thursday.
The UK Foreign Office had earlier announced it would shut its mission in the Yemeni capital Sanaa until Tuesday.
Meanwhile US diplomat missions in Algiers, Kabul and Baghdad are among those which will reopen on Monday, Washington said.
But its diplomatic posts in Abu Dhabi, Amman, Cairo, Riyadh, Dhahran, Jeddah, Doha, Dubai, Kuwait, Manama, Muscat, Sanaa and Tripoli will remain closed until Saturday.
The US state department also added African missions in Antananarivo, Bujumbura, Djibouti, Khartoum, Kigali and Port Louis to the list, meaning a total of 19 US embassies will be closed this week.
A state department global travel alert, issued on Friday, is in force until the end of August.
The department said the potential for an al-Qaeda inspired attack was particularly strong in the Middle East and North Africa.
Embassies closed on Sunday, a working day in the Muslim world, included Amman, Cairo, Riyadh and Dhaka.
The embassy closures and US global travel alert came after the US reportedly intercepted al-Qaeda messages.
It has been suggested that they were between senior figures talking about a plot against an embassy.
