More demonstrations in Cairo and elsewhere in Egypt are expected following the killing of more than 50 supporters of deposed president Mohammed Morsi.
The warning came in an updated advisory from the Foreign & Commonwealth Office yesterday.
More than 300 people were also injured in the deadly incident between the army and Muslin Brotherhood protestors.
The FCO continues to recommend against all but essential travel to Egypt except for resorts on the Red Sea.
“Further demonstrations are likely, and there is a risk of violence. Demonstrations often happen on Fridays. The atmosphere of these demonstrations can change quickly and without warning,” the FCO said.
It warned of violent clashes between opposing groups and security forces following the removal of Morsi from office almost a week ago.
Thirty six people were killed and more than 1,000 injured on Friday.
Most of the casualties were in Cairo and Alexandria, but there have also been clashes elsewhere, in particular, Luxor, Assyut, Suez, Ismaliyya, and Qena, according to the FCO.
“The Red Sea resort of Hurghada saw limited protests and there are no reports of violence,” it added.
The update came as Egypt’s interim leader outlined a timetable for new elections.
Adly Mansour’s decree envisages changes to the Islamist-drafted constitution and a referendum, which would pave the way for elections early next year.