Twelve Chinese big data companies, including Internet giant Alibaba, vowed to better protect user data, as they signed a proposal on Monday in the city of Hangzhou in east China's Zhejiang Province.

Signatories also included another Internet heavyweight Netease and the provincial branches of three major telecommunication operators in the country.

In the jointly-signed proposal on private information protection, the firms promised to guarantee users' control over their information and will clearly explain how they handle their information. The firms also promised not to force users to authorize their data to them.

The enterprises pledged to deal with user data in a transparent way and will inform users if any data leaks occur, according to the proposal.

The companies also agreed to establish a mechanism to allow users to have access to their data and make sure users can update and delete their private information.

The signatories said they will not collect, store, use or share user data without the knowledge of their clients, and vow to shield user data with better security technology and management.

The proposal was signed during the ongoing "cybersecurity week" in Zhejiang Province.

The number of Internet users in China hit 802 million at the end of June, up 3.8 percent from six months ago, according to a report from the China Internet Network Information Center in August.