HANGZHOU, China In an abrupt move, Alibaba has removed thepresident of its video streaming business Youku.

In a securities filing on Tuesday, Alibaba named Luyuan Fan as president of Youku, replacing Weidong Yang whilevirtually accusing him of unethical or unlawful conduct.

Yang had been with Youku in various capacities for five-and-a-half years, having joined the group in March 2013. At the time of his removal on Tuesday, the platform had 500 million active users.

It is undertstood Yang has been arrested and is under police investigation in China for alleged acceptance of improper payments.Mr.Yang was arrested by police on Monday.Alibaba Group said it is cooperating fully with the investigation.

In November, Mr.Fan had previously replaced Mr.Yang as rotating president of Alibaba Groups digital media and entertainment business, which includes Youku and other businesses, Alibaba said in its US Securities and Exchange Commission filing Tuesday.

Alibaba Group is committed to the highest standards of business conduct in our relationships with each of our stakeholders, including our customers, business partners and shareholders.

We require all employees to conduct our business in accordance with all applicable laws and regulations and in accordance with the Alibaba Group Code of Business Conduct.We do not tolerate any form of unethical or unlawful conduct, said the Alibaba SEC filing.