A female suspect named Gao Yu was detained for leaking "state secrets" to foreign contacts, said Beijing police on Thursday.

Gao, a Beijing resident aged 70, was suspected of illegally obtaining a highly confidential document and sending an electronic copy of it to an overseas website in June last year, said the police statement.

The document was later published at the website and widely reposted abroad, the statement said.

Police detained her on April 24 and seized substantial evidence at her residence, it said.

Gao expressed deep remorse about what she did.

The police statement quoted her as saying that she deeply regretted that her behavior harmed the nation's interests and violated the law, and she is willing to accept punishment from the law.

The case is still under further investigation, it said.

Gao was sentenced in 1993 to six years in prison for leaking state secrets.