The UK has suspended flights to and from Sharm el-Sheikh after No 10 said there is a "significant possibility" that a Russian plane was brought down by an explosion.
Foreign Secretary Philip Hammond says "emergency procedures" for additional screening and security measures at Sharm el-Sheikh airport will be put in place.
ITV News Presenter Julie Etchingham looks into the security situation in Sharm el-Sheikh:
Four soldiers were killed and nine wounded when gunmen attacked a military bus today that was travelling in the Sinai Peninsula, security sources said.
Sinai-based militants have stepped up violence against the state since Islamist President Mohamed Mursi's ouster in July, and the attacks have become more brazen in recent months.
At least two people were killed and 14 wounded early on Monday in Egypt's North Sinai province when suspected militants used rocket propelled grenades to attack a bus carrying workers employed at a cement factory, security and medical sources told Reuters.
They said the bus was fired on in the city of El Arish, at the centre of a sharp rise in Islamist militant attacks in the lawless region bordering Israel and the Gaza Strip since President Mohamed Morsi was ousted by the military on July 3rd.
Islamist gunmen have staged multiple attacks on security forces in Egypt's troubled Sinai Peninsula, security sources and state television reported.
The security sources said a soldier was killed and two were wounded when a police station in Rafah on the border with the Gaza Strip came under rocket fire. The police post is close to the local headquarters of military intelligence.
It was not clear whether the attacks were coordinated and in reaction to Mohamed Morsi's removal as president.
Egyptian police clashed with armed men in northern Sinai today, according to state television. The clashes come a day after security forces began a crackdown on Islamist militants in the area. Nile News Television told Reuters: