BEIJING - China's quality supervisor on Friday issued an alert for defects in air bags and other safety devices of some BMW and Rolls-Royce cars.

Airbags, safety belts and active head restraints of some cars of the two brands will not work during collisions, said an online statement of the General Administration of Quality Supervision, Inspection and Quarantine (GAQSIQ).

The defective vehicles involve 17,327 BMW 7 series, 5,216 BMW 5 series and 336 Rolls-Royce Ghost built in 2011 and 2012.

The GAQSIQ advised car owners to stop driving those models and asked the BMW to launch a recall as soon as possible, adding that it will closely watch the progress.

It also asked Rolls-Royce dealers to repair these defects free of charge.