BEIJING (Reuters) - Complaints about BYD over its move to offer free smart driving features across most of its line-up have flooded a prominent Chinese auto quality platform, many from customers who said they had overpaid for their cars.

Over 4,700 complaints were filed against BYD cars between February 11-17 on 12365auto.com, a third-party auto consumer complaints platform, compared with about 150 the week before and roughly 500 for January.

BYD cars, including ones from its best-selling Ocean and Dynasty series, also took the top 10 spots on a list the platform publishes that ranks models by the number of complaints received.

One complaint, sent in by an owner of a Seal 06 DM-i plug-in hybrid sedan, said they had repeatedly asked the salesperson when buying the car if a newer model would be launched this year.

"But only half a month after I picked up the car, the new model hit the market with notable upgrades in configuration at the same price," the person said, adding that they wanted free upgrades and other compensation from the company.

The platform showed BYD responding to say that the company had passed on the complaint to the relevant company departments.

BYD did not respond to a request for comment.

The complaints are one of the ripple effects a prolonged price war and hyper competitiveness in the Chinese market are having as automakers slash prices, offer free features or incentives, or roll out new models at a pace faster than other countries.

Two years ago, U.S. automaker Tesla, shortly after it cut prices in a move that started the price war, saw hundreds of Tesla owners assemble at the company's showrooms and distribution centres in China, seeking rebates and credits.