BMW is voluntarily recalling 350,000 cars worldwide due to a possible brake problems that the world's biggest premium carmaker said have not caused any accidents.

In some cars brake fluid has leaked into the hydraulics, preventing pressure from building up. The customer notices this since he needs to apply more pressure to the brake, but the brakes still work, a company spokesman said on Friday.

Chief Financial Officer Friedrich Eichiner told Reuters he did not expect repairs to require great technical effort but he did not yet have an estimate on how much the recall would cost.

BMW's problem, which tended to occur among vehicles with high mileage, was discovered in models equipped with the eight- and 12-cylinder engines popular in the United States.

Around 345,000 BMW brand 5, 6 and 7 Series models built since 2002 are being recalled worldwide. Of that, almost 200,000 are owned by U.S. residents.

A spokesman for BMW's luxury brand Rolls-Royce said it was unaware of any problems so far in its Phantom family that use exclusively 12-cylinder engines. Rolls-Royce customers tend to own many cars and hence mileage is typically much lower.

Nevertheless, Rolls-Royce will ask all 5,800 Phantom customers to bring their vehicles to a garage for inspection.

No Rolls-Royce Ghosts were impacted, the spokesman said.

BMW shares fell 2 percent by 1248 GMT, lagging an 0.7 percent decline in the STOXX European car sector index .SXAP.

Recalls typically are more damaging to a brand's image than to its bottom line due to provisions booked with the sale of vehicles.

BMW's move is not a recall in the strictest sense, a term generally reserved for a compulsory measure required by the National Highway Traffic Safety Administration (NHTSA), often in conjunction with serious safety issues.

Forced recalls can lead to a public relations disaster for a company, as Toyota Motor Corp discovered after issues with unintended acceleration in some models made the Japanese carmaker recall millions of vehicles.

(Reporting by Irene Preisinger and Christiaan Hetzner; Editing by Michael Shields)