Rescuers are searching for a Malaysia Airlines Boeing 777 with 239 passengers and crew on board which went missing while flying between Kuala Lumpur and Beijing.
The flight was a codeshare with China Southern Airlines and more than 150 of the 227 passengers were from China.
There were 14 different nationalities on board, including 38 Malaysians, 12 people from Indonesia and six from Australia.
Chinese state media reported that two rescue boats have been sent into the South China Sea, from the ports of Haikou and Nansha, to assist with the search and rescue effort.
The aircraft went off the radar south of Vietnam, according to a statement on the Vietnamese government website. The weather along the route was reportedly good.
MAS said that flight MH370 had disappeared at 2.40am local time on Saturday after leaving Kuala Lumpur.
The airline’s chief executive Ahmad Jauhari Yahya said the focus was on helping the families of those missing. He said that 80% of families had been contacted.
Malaysia’s transport minister said there was no information on wreckage and he urged against speculation, the BBC reported.
“We are doing everything in our power to locate the plane. We are doing everything we can to ensure every possible angle has been addressed,” Seri Hishammuddin said.