Egypt's president has called for a state of emergency after suicide bombers killed at least 44 people at two Coptic churches on Sunday.
Following the attacks, the Foreign and Commonwealth Office (FCO) issued updated travel advice for Egypt.
Describing the bombings in Tanta and Alexandria, it said "many people" had been killed and advised: "You should remain vigilant at all times and follow the advice of local security officials, including in and around religious sites and during religious festivals."
The FCO advises against all travel to the Governorate of North Sinai due to the significant increase in criminal activity and deadly terrorist attacks on police and security forces.
All but essential travel is advised against to the Governorate of South Sinai, with the exception of the area within the Sharm el Sheikh perimeter barrier, which includes the airport and the areas of Sharm el Maya, Hadaba, Naama Bay, Sharks Bay and Nabq.
However, the FCO advises against all but essential travel by air to or from Sharm el Sheikh, with the UK Government warning of a "heightened risk of terrorism against aviation". There have been no direct flights from Sharm to the UK since a flight from there to St Petersburg crashed in North Sinai in October 2015, with investigators concluding that it was caused by an explosion on-board.
The area west of the Nile Valley and Nile Delta regions, excluding the coastal areas between the Nile Delta and Marsa Matruh, should also be avoided, according to the FCO.
It says there is a "high threat from terrorism" in Egypt.