Second Qantas jet grounded after engine problems

A Qantas 747 plane has been grounded in Singapore after it was forced to make an emergency landing in the city - the second such incident involving the Australian airline in two days.

The Sydney-bound Boeing 747-400 with 412 passengers on board had been in the air for about 20 minutes when it sought "immediate clearance" to return to Singapore, a Qantas spokeswoman said.

However, passengers on board the plane indicated the problem was more serious. Passengers who spoke to Reuters said they saw flames coming from one of the 747's engines, while Singapore's Channel NewsAsia quoted other passengers as saying they smelt burning fuel and saw smoke.

Some of those on board the Boeing had even been on the A380 that made an emergency landing the day before.

In a similar incident on Thursday, a Qantas Airbus A380 returned to make an emergency landing in Singapore after an explosion in an engine shortly after take-off. The engine failure on Thursday, which scattered debris on an Indonesian island, was the most serious incident affecting the world's largest passenger plane, which has been in service since 2007.

Qantas grounded its fleet and other airlines carried out checks on their own A380s.

Qantas said a faulty part or design fault might have caused the damage to the A380's engine, which was made by Rolls-Royce. The manufacturer of the Qantas 747's engine was not immediately known.