A veteran Chinese journalist has been jailed for seven years for leaking a document detailing the Communist Party's resolve to target civil press freedom as a threat to its monopoly on power.

The sentence against Gao Yu, 71, comes amid a widening clampdown on free speech that highlights the gap between China's vision of rule of law and Western notions of civil liberties and judicial fairness.

The document Gao was convicted of leaking, deemed a state secret, underpins the crackdown under the administration of Communist Party leader Xi Jinping.

The Beijing court verdict appears to confirm the authenticity of the leaked document, which had been reported since June 2013 but was never discussed openly by the leadership.

It verifies widely held assumptions about Mr Xi's distrust of any social organisation outside party control.

That was recently shown by the more-than month-long detentions of five women's rights activists who planned to start a public awareness campaign about sexual harassment.

Gao had denied the charges. Her lawyer Mo Shaoping said Gao was convicted of leaking state secrets by giving the strategy paper, known as Document No. 9, to an overseas media group.

The document argued for aggressive curbs on the spread of Western democracy, universal values, civil society and press freedom, which the party considers a threat to its rule.

Another of her lawyers, Shang Baojun, said Gao did not speak during the verdict and sentencing, and added that they would definitely appeal.

Police patrolled the perimeter of Beijing's No. 3 Intermediate Court where the verdict was delivered. Journalists and foreign diplomats gathered at the court but were denied entry to the hearing.

"We're obviously disappointed with the verdict," said US embassy first secretary Dan Biers.

Gao, who wrote about politics, economics and social issues for media in Hong Kong and overseas, has already served time in prison on state secrets charges more than two decades ago.

Amnesty International said Gao was the victim of vaguely worded and arbitrary state secrets law that is often used against activists to quell freedom of expression.

"This deplorable sentence against Gao Yu is nothing more than blatant political persecution by the Chinese authorities," said William Nee, the group's China researcher.