Prime Minister Lee Hsien Loong wrote to his Malaysian counterpart Najib Razak and China's Premier Li Keqiang on Friday to express solidarity and offer support, as the search for a missing Malaysian Airlines flight continued.

There were many Malaysians on board but the largest group were passengers from China, several of whom had studied or worked in Singapore, PM Lee said in a Facebook post on Friday night.

He added: "Disturbing that #MH370 is still missing after a week. The families of the passengers and crew must be distraught with anxiety and grief."

He said he had been tracking the matter closely, and that Singapore's ships and aircraft were participating in the search.

"Hope the plane will be found soon," PM Lee added.

The flight, MH 370, dropped off the radar soon after leaving Kuala Lumpur for Beijing last Saturday.