Vietnamese rescue planes have spotted large oil slicks and a column of smoke off its coastline, but it was not clear if they were connected to a missing Malaysia Airlines carrier, a transportation ministry official said on Saturday.

The Malaysia Airlines Boeing 777-200ER plane carrying 227 passengers and 12 crew went missing off the Vietnamese coast early on Saturday as it flew from Kuala Lumpur to Beijing and was presumed to have crashed.

"Vietnam rescue airplanes saw two oil spills and one smoke column in the area around 250 km west of Tho Chu island, but we can't confirm it's from that Malaysia plane," Pham Quy Tieu, vice minister of transportation, told Reuters by telephone.

"We sent two maritime boats and some military boats there to clarify, each boat with about 20 people. The oil spills are about 15km long. Those boats will be there in about three to four hours."

There were no reports of bad weather and no sign why the Malaysia Airlines plane would have vanished from radar screens about an hour after take-off.

A large number of planes and ships from several countries are scouring the area where the plane last made contact, about halfway between Malaysia and the southern tip of Vietnam.-Reuters