China has vowed never to let Malaysia face the current unprecedented disappearance of a Malaysia Airlines (MAS) aircraft alone.

Its ambassador to Malaysia, Huang Huikang said China was committed to help and trust Malaysia's efforts in handling the situation which he described as a consistent commitment from the beginning.

"Our relations had never been affected by any unexpected single incident. Through the cooperation in dealing with the incident, our relations have become stronger and closer.

"These (have) once again proved a friend in need, is a fiend indeed," he said at a press briefing in conjunction with the 40th anniversary of diplomatic relations between China and Malaysia here Thursday.

On March 8, MAS Flight MH370 disappeared with 227 passengers and 12 crew members on board the Boeing 777-200ER aircraft. Almost two-thirds of the passengers are Chinese nationals.

"If you look at the progress that has been made in dealing with the incident from the very beginning, the Chinese Government and its people firmly stand side by side with Malaysia," said Huang.

He added that China had organised a large-scale international search and rescue operation, as well as mobilised a number of satellites, ships and aircraft.

He said China had put so much effort to deal with the MH370 incident because two-thirds of the passengers were its citizens.

"It is the Chinese Government's responsibility, no matter how much money we have spent, we are doing our best to assist Malaysia," he said.

Malaysian Prime Minister Datuk Seri Najib Razak is scheduled to visit China from May 27 until Jun 1, to mark the 40th anniversary relations.

Huang said the Chinese Government had put a lot of effort and attention as the visit would further enhance bilateral relations of both countries.