Fishermen have reportedly found a life raft floating in waters off Port Dickson, a southwestern Malaysian port town.

The discovery raised hopes of a breakthrough in the search for the missing Malaysia Airlines flight MH370, but authorities could not retrieve the raft.

The fisherman notified the maritime authorities after they found the floating object bearing the word "Boarding" around 10 nautical miles from Port Dickson, the New Strait Times reported.

"We managed to tie it to our boat as we feared it would sink due to the damages," 40-year old fisherman Azman Mohamad told the Malaysian daily. As the raft was very heavy the fishermen could not lift it, and waited for the arrival of authorities.

Port Dickson, south of Kuala Lumpur, is on the Strait of Malacca, on Malaysia's western coast.

Malaysia's air force chief has denied reports that quoted him as saying the military radar had tracked the jetliner over the Strait of Malacca.

The search personnel of the Malaysian Maritime Enforcement Agency (MMEA) in Malacca rushed to the area, but the raft is said to have sunk in the sea by the time they arrived.

Attempts are now being made to salvage the craft, according to reports.

Similar findings have been reported on many previous occasions during the four-day-long search, but hopes were dampened each time as the objects were declared unrelated to the missing aircraft.

The Beijing-bound passenger aircraft, which originated in Kuala Lumpur, vanished on Saturday with 239 people on board and remains untraceable.