WASHINGTON (AFP/REUTERS) - Two Air France flights that took off from the United States on Tuesday (Nov 17) were later diverted due to security issues, the US Federal Aviation Administration and media reports said, on the heels of deadly terror strikes in Paris.

One flight, AF55 from Dulles International Airport near Washington, DC to Paris, was diverted to Halifax, Nova Scotia, according to US broadcasters CNN and NBC and Canada's CBC.

The flight was diverted to Halifax International Airport in Nova Scotia because of an unspecified security concern, the FAA said.

Halifax airport spokesman Peter Spurway said the Air France Boeing 777 jet was diverted to Halifax at 10.15pm eastern time and was sitting at the end of the airport's main runway.

"It's an RCMP matter," Mr Spurway said, referring to the Royal Canadian Mounted Police. "The passengers are being deplaned at this point and being transferred to a secure area of the terminal building because they're international passengers."

The Royal Canadian Mounted Police in Halifax said on its Twitter feed that it was responding to a bomb threat against the Air France plane that had landed there.

"RCMP will be searching the Air France plane using police dogs trained in explosives," RCMP Nova Scotia said in a tweet.

The other, AF65 from Los Angeles to the French capital, was diverted to Salt Lake City. The Airbus A-380 landed in Salt Lake City, where passengers and crew were being deplaned and transferred to the terminal, an FAA spokesman said.

CNN, citing a US government official, reported that Flight 65 was diverted after a bomb threat was called in from the ground. The official did not know if anyone had been arrested in connection with that incident.

"Several law-enforcement agencies are working in concert, following established protocol, to determine the nature of the threats which caused the aircraft to divert," FBI special agent Todd Palmer, of the agency's Salt Lake City division, told the network.

Both planes have landed and passengers disembarked, reports said.

In a brief statement, Air France said both flights had been the "subjects of anonymous threats received after their respective take-offs".

"As a precautionary measure and to conduct all necessary security checks, Air France, applying the safety regulations in force, decided to request the landings of both aircraft," the airline said in its statement.

"Local authorities are carrying out complete inspections of the aircraft, their passengers and their luggage," the statement said. "An investigation will be led by the authorities to identify the source of the telephone call."

An FAA spokesman confirmed to AFP that flight 65 was diverted to Salt Lake City. "It landed safely," she said, but declined to comment on the reported security threat.

"Passengers are being removed from flight. No word on why flight diverted," Canada's CBC said on Twitter of the jet that landed in Nova Scotia.

Mr Keith Rosso, who tweeted a photo shortly after take-off from Los Angeles, said: "Thankful to everyone who has been working to keep everyone calm and make sure air travel is safe. Hope to be taking off again shortly."

The incidents did not appear to be causing flight delays or cancellations elsewhere.

According to data on flight tracking website flightradar24.com, flights operated by both Air France and other airlines appear to be taking off and landing normally at Charles de Gaulle Airport in Paris.

Social media comments alluded to an emergency landing of the jet that left Los Angeles, saying it had touched down in Utah, with many police cars on the tarmac.

Security officials have been on high alert since last week's deadly attacks in Paris, claimed by Islamic State in Iraq and Syria militants, killed 129 people, and after Russia said the group was responsible for the downing on Oct 31 of a plane returning to St Petersburg from the Sharm al-Sheikh resort in Egypt, killing all 224 on board.