British Airways abruptly suspended all flights to Cairo for a week from Saturday over security concerns, giving no details about what prompted the move.

"We constantly review our security arrangements at all our airports around the world, and have suspended flights to Cairo for seven days as a precaution to allow for further assessment," the statement said.

The airline added that it would never operate an aircraft unless it was safe to do so. When asked for more details about why flights had been suspended and what security arrangements the airline was reviewing, a spokesperson for the airline responded: "We never discuss matters of security."

German airline Lufthansa later said it had also cancelled its flights to Cairo on Saturday from Munich and Frankfurt and will resume its flights on Sunday.

Three Egyptian airport security sources told Reuters that British staff were checking security at Cairo airport on Wednesday and Thursday. They provided no further details.

The British Foreign Office (BFO) updated its travel advice on Saturday to add a reference to the British Airways suspension, advising travellers affected to contact the airline.

The British government has long advised against all but essential travel by air to and from the Egyptian resort of Sharm el-Sheikh, where a Russian passenger jet was bombed in 2015, but has not issued similar warnings against air travel to and from Cairo.

Currently about to board a <a href="https://twitter.com/British_Airways?ref_src=twsrc%5Etfw">@British_Airways</a> flight to Cairo and it’s cancelled. Not for a day. Not for two days but for seven. Security risk. Someone knows something we don’t. <a href="https://t.co/oGQsSByP35">pic.twitter.com/oGQsSByP35</a> —@shanghai_dan

"There's a heightened risk of terrorism against aviation. Additional security measures are in place for flights departing from Egypt to the U.K.," the BFO said.

Egypt's Ministry of Civil Aviation said in a statement late on Saturday that it had contacted the British Embassy in Cairo which had confirmed that the decision to suspend the flights was not issued by Britain's transport or foreign ministries.

The ministry added that it will add more flights from Cairo to London starting tomorrow "to facilitate transporting passengers during this period."

However, Egyptian officials on Saturday say Cairo's international airport has been notified by British Airways that the airline is suspending flights to and from London for two days.

A person is seen walking in the Cairo International Airport in October 2016. British Airways has not explained why it has suspended flights into or out of the airport. (Amr Abdallah Dalsh/Reuters)

Airport officials say the decision came after British officials conducted regular security checks earlier this week at the airport. There were no additional details.

The officials said all other airlines were operating as usual at the airport. They spoke to the Associated Press on condition of anonymity because they were not authorized to brief reporters.

Tourism, a key source of foreign revenue for Egypt, has been recovering after tourist numbers dropped in the wake of a 2011 uprising and the 2015 bombing of the Russian passenger jet, which killed all 224 people on board shortly after takeoff.

That attack, which was claimed by Islamic State, prompted Russia to halt all flights to Egypt for several years and a number of countries, including Britain, to cease flights to Sharm el-Sheikh, which have yet to resume.

The moves come as Britain weighs its response to Iran's seizure Friday of a British-flagged oil tanker in the Strait of Hormuz and rising tensions stemming from U.S. sanctions' effect on Iran's economy and oil exports.

The strait and the Egyptian capital are separated by 2,500 kilometres and Egypt has long had a contentious relationship with Iran.