BYD Co Ltd 002594.SZ(1211.HK), the Chinese carmaker backed by Warren Buffett, said on Wednesday its chairman has increased his stake in the company and may buy more shares as a sign of confidence following the stock's record slump last week.

Wang Chuanfu, BYD's chairman, president and CEO, bought one million of BYD's Hong Kong-listed shares on Tuesday, raising his stake in the company to 23.1 percent, BYD said in statements posted on the Shenzhen and Hong Kong stock exchanges.

"Mr Wang has indicated that he does not rule out the possibility of further increasing his shareholding in the company if and when appropriate in the future," BYD said.

The move shows that Wang "has confidence toward the future prospects of the company," according to the statements.

BYD's Hong Kong shares fell 29 percent on Thursday in record trading, logging their biggest one-day drop, in an unexplained slide that wiped out around $1.2 billion of its market capitalization.

The shares have since stabilized after BYD held calls with analysts and issued statements saying the company's fundamentals remained healthy.

BYD's statements came after the China and Hong Kong markets closed.

On Wednesday, its shares rose 3.5 percent, outperforming the main Hang Seng Index's .HSI0.07 percent rise, while its Shenzhen stock was up 4.3 percent versus the Shenzhen composite index's .SZSME 1.8 percent gain.