LONDON (REUTERS, AFP, BLOOMBERG) - British Airways and Lufthansa abruptly suspended flights to Cairo from Saturday (July 20) over security concerns, but giving no details about what may have 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," British Airways said in a statement.

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

British Airways, a unit of IAG, also said 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 spokeswoman responded: "We never discuss matters of security."

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.

Youssef Chouhoud, a political scientist at Christopher Newport University in Virginia, said on Twitter that his flight to Cairo from London's Heathrow Airport had been cancelled.

He asked why other airlines were not taking similar precautions.

"What does @British-Airways know about the security situation in Cairo that we don't??" he said.

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

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."

In its travel advice for British nationals heading to Egypt, the Foreign Office in London warns: "There's a heightened risk of terrorism against aviation.

"Additional security measures are in place for flights departing from Egypt to the UK. You should co-operate fully with security officials at airports."

Britain advises against all but essential travel by air to or from the Red Sea resort of Sharm el-Sheikh on the Sinai peninsula.

"Terrorists are very likely to try to carry out attacks in Egypt. Although most attacks occur in North Sinai, there is a risk of terrorist attacks across the country," Britons are warned.

"Terrorists in Egypt likely maintain the intent and capability to target aviation.

"The greatest threat is on the Sinai peninsula where Daesh operate with greater freedom, but terrorists are active in mainland Egypt, including Cairo."

The Foreign Office warns that it "can't offer advice on the safety of individual airlines".

An estimated 415,000 British nationals visited Egypt in 2018.