Possible debris from the vanished Malaysia Airlines flight MH370 has been found in the sea off Vietnam by a search team, a senior official says.

It is the first time authorities have given any positive indication that traces of the Boeing 777, which disappeared in the early hours of Saturday carrying 239 people, may have been discovered.

"We received information from a Vietnamese plane saying that they found two broken objects, which seem like those of an aircraft, located about 50 miles to the south-west of Tho Chu Island," said the senior from official from the National Committee for Search and Rescue, who did not want to be named.

An oil slick spotted in the sea off Vietnam which authorities believe may be jet fuel. Photograph: Tienphong.vn/EPA

"As it is night they cannot fish them out for proper identification. They have located the position of the areas and flown back to the land," he added.

Planes and boats would be sent back to the area on Monday to investigate further, he said.

Tho Chu island is part of a small archipelago off the south-western tip of Vietnam which belongs to the communist country.

Two large oil slicks which authorities suspect were caused by jet fuel were detected late on Saturday further south off the island chain.