The British Foreign and Commonwealth Office said Friday it was advising against all travel to North Sinai and all but essential travel for the rest of the country.
"This is in view of continued unrest and the evolving political situation in Egypt," it said.
The Cairo government said it expected widespread protests to erupt across much of the country ahead of the start of trial for deposed President Mohamed Morsi Monday. The advisory warned there was a "serious risk of violence and sexual assault at demonstrations."
Morsi, removed from power by the military in July, is facing several charges, including murder. Ahram Online, an Egyptian news service, said pro-Morsi demonstrators took to the streets in Cairo and elsewhere following Friday prayers. It said major demonstrations were planned by a pro-Morsi alliance Monday.
An overnight curfew is in place across much of the country. The British travel advisory warns that, apart from the demonstrations, there is a "high threat from terrorism" across Egypt.