Mystery surrounds a Malaysia Airlines flight which disappeared over the South China Sea with six Australians onboard.

Three Australian couples and a New Zealander living in Perth are feared dead more than 24 hours after a Malaysia Airlines plane carrying 239 people disappeared over the South China Sea.

Authorities are examining links to terrorism, with two of the flight’s passengers found to be using stolen passports.

Flight MH370 lost contact with air traffic controllers early Saturday morning and vanished from radar screens just over two hours into what should have been a six-hour red-eye flight from Kuala Lumpur to Beijing.

The weather was fine and no distress signals were received but radar signals indicate the jet may have turned back.

Another pilot, flying ahead of the missing plane, made contact but only heard mumbling and static from the cockpit.

So far only two oil slicks have been discovered, the first sign the aircraft has crashed.

The search has been expanded and half a dozen nations have joined the operation.

Four people on the plane are being investigated and the FBI has also been called in to review video of departing passengers that can be checked against its vast counter-terrorism database.

Queensland couples Robert and Catherine Lawton and Rodney and Mary Burrows are amongst those missing.

The Burrows’ neighbours, who didn’t want to be named, are dumbstruck by the tragedy and have begun grieving. They raised families side by side for 20 years in the close-knit Middle Park, in Brisbane’s southwest.

Mr Burrows took a redundancy last year and they moved away just weeks ago to a smaller house to enjoy retirement and travel with the Lawtons.

“They basically moved into a new chapter of their life,” the neighbour told AAP.

“They were beautiful people and we loved them dearly.

“Hopefully it was quick for them.”

The Lawtons are parents of three and dotting grandparents of two.

At their Springfield Lakes home two wooden signs are proudly placed at their front door: “Nanny and Poppy’s House, Grandchildren welcome anytime, open 24 hours.”

The other read: “Where memories are made and grandchildren spoilt.”

Neighbour Ziba Kalntary had been following events unfold on the internet.

“They were very kind,” she said.

“It’s very, very sad and I don’t know what I can do, just pray for all of them.”

Sydney couple Yuan Li and Naijun Gu, from Sutherland Shire, were also aboard the plane as well as New Zealander Paul Weeks who was residing in Australia.

The 39-year-old and his wife Danica moved to Perth from earthquake-ravaged Christchurch in 2011.

Mr Weeks, a mechanical engineer, was travelling to Mongolia for his first shift in a fly-in-fly-out job.

Prime Minister Tony Abbott described the tragedy as a “horrible, horrible business”.

“Our thoughts and prayers are with the passengers and their families on that ill-fated aircraft, particularly to the six Australian passengers and their families, that have now been confirmed to be on board,” he said in Adelaide.