Passengers said they heard a bang and saw flames coming from the aircraft's engine minutes after takeoff [AFP]

A second Qantas Airways jet has been forced to abort its journey to Sydney after an engine caught fire just minutes after taking off from Singapore.

The Boeing 747-400 returned for an emergency landing early on Friday morning just 20 minutes after takeoff.

This second incident comes less than 48 hours after another of the Australian carrier's aeroplanes was forced to land prematurely due to engine failure.

In the earlier incident on Thursday, a Qantas Airbus A380 jet made an emergency landing after one of its four Rolls-Royce engines appeared to break apart in flight, scattering debris over an Indonesian island.

'Jet of fire'

Andrew Jenkins, an Australian banker, told The Associated Press in a telephone interview: "There was a loud bang and a jet of fire from the back of the engine."

Jenkins said the blast happened "one or two minutes" into the flight after the aeroplane had climbed about 600 metres.

Qantas said in a statement that the captain of flight QF6 - which had 412 passengers, three flight crew and 16 cabin crew on board - immediately sought priority clearance to return to Singapore "as a precaution".

Thursday's A380 engine failure was the biggest incident to date for the world's largest passenger plane, which went into service in 2007.

Source: Agencies