Image caption Airbus said there was no immediate threat to safety

Twenty Airbus A380s will have to undergo checks for cracks in their wings, the safety regulator has said.

The European Aviation Safety Agency (EASA) said the planes, a third of the current fleet, would undergo a "visual inspection" for cracks.

A few planes, which have carried out more than 1,800 flights, will need inspections within four days, it said.

Airbus said the cracks were not an immediate threat to safety. If cracks are found it will carry out repairs.

The problems could affect planes operated by Singapore Airlines, Emirates and Air France.

Cracks

The agency said it has determined that the cracks may develop on aeroplanes after a "period of time" in service.

"This condition, if not detected and corrected, could potentially affect the structural integrity of the aeroplane," said the agency in its directive ordering the inspections.

This is the second set of cracks found on A380 wings.

The first, which were less serious, emerged during repairs to a Qantas A380 following a blowout of its Rolls Royce engine in November 2010.

That prompted more widespread investigations and more serious cracks were found in the UK-made wings on Thursday.

If more, similar, cracks are found aircraft may be grounded in order to carry out a repair programme agreed between Airbus and regulators.

Repairs

Only planes which have carried out more than 1,800 flights are being targeted urgently, those which have flown between 1,300 and 1,800 flights must be tested within 6 weeks.

"Airbus confirms that during routine inspections some additional cracks have been found on a limited number of non-critical brackets (known as rib-skin attachments or wing rib feet) inside the wings of some A380s," the company said in a statement.

However EASA warned further steps may be needed.

"As a result of the on-going investigation, further mandatory action might be considered."