BEIJING (REUTERS) - Chinese relatives of those on board Malaysia Airlines Flight MH370, which went missing two years ago on a flight to Beijing, made an emotional plea on Friday (July 29) for the search to continue.

Last week, Malaysia, China and Australia said in a joint statement that the hunt for MH370 would be suspended if the aircraft was not found in an area now being searched.

The Boeing 777, with 239 aboard, disappeared in March 2014 while on a flight from the Malaysian capital, Kuala Lumpur.

Almost A$180 million (S$182 million) has been spent since then on an underwater search spanning 120,000 square kilometres in the southern Indian Ocean.

About 30 family members, some in tears, gathered at China's foreign ministry to hand over the petition, and a group were allowed in despite a brief stand-off with plainclothes security.

"We oppose their decision. We don't recognise it at all. That decision has no reason behind it," said Boa Lanfang, 65, whose son, daughter-in-law and grandson were on the flight.

Some family members held up placards reading "The three governments have an obligation to the world to fulfil their promise".

The families of those on board, most of whom were from China, have pressed hard for answers ever since the plane went missing.

China's Foreign Ministry did not immediately respond to a request for comment.

Investigators believe the plane was deliberately flown thousands of kilometres off course before crashing into the southern Indian Ocean off Australia.

Malaysian investigators said in 2015 there was nothing suspicious in the financial, medical or personal histories of pilots or crew.

Several pieces of aircraft wreckage have washed up on beaches in Africa and been positively identified as coming from MH370 but they shed little light on the mystery.

The search has lasted more than two years but has found no sign of the main wreckage.