The Foreign & Commonwealth Office (FCO) urges all British expats, business travellers and tourists to keep away from the area.
Only the tourist resorts of Sharm el Shiekh are given the all clear on the Sinai peninsula due to an increased military presence and extra checkpoints at airports.
On May 2, two bombs exploded – one at El Tor in South Sinai and the other at Heliopolis, Cairo. In April, bombs went off at Cairo University.
In earlier incidents, tourists have died in bomb blasts and the terror groups claiming responsibility warn further attacks are planned.
“We understand the terrorists are willing to continue their activities,” said an FCO spokesman.
“The attacks are indiscriminate and without warning mainly targeting government buildings. Travellers should take care near police, military and government sites and attacks against foreigners cannot be ruled out.”
MERS virus still spreading
Meanwhile, a suspected case of Middle East Respiratory Syndrome (MERS) was diagnosed on a passenger flying through London from the Saudi Arabian capital of Riyadh to Chicago.
The Saudi authorities have identified 18 new MERS cases, taking the number of victims to more than 450.
So far, more than 120 people have died from the infection in Saudi Arabia, mainly in Jeddah and Riyadh.
Doctors are treating cases in 12 other countries, mainly in the Middle East, but including France, Britain, Spain and Italy.
“Travellers should take precautions as the disease is partly spreading because of the lack of preventive measures in hospitals,” said a World Health Organisation spokesman.
MERS symptoms include coughing, pneumonia and fever.
The FCO is also warning travellers to stay away from the Turkish border with Syria due to tension between the armed forces on both sides.
The Turkish air force has recently shot down a Syrian fighter and confrontation between troops has led to skirmishes along the border.
Travellers should stay from the towns of Akcakale and Ceylanpinar, says the FCO.
The FCO also warns of civil unrest in Istanbul, where demonstrations in the Sisi neighbourhood have ended with police dispersing large crowds of demonstrators with tear gas and water cannon. One demonstrator was shot dead by police.
Similar protests on a much smaller scale have taken place in other cities.