A Chinese court has sentenced a 71-year-old female journalist to seven years in jail for leaking state secrets, in a case seen by rights groups as part of a crackdown on government critics.

Gao Yu, named one of the International Press Institute's 50 "world press heroes" in 2000, "illegally provided state secrets to foreigners", Beijing's No 3 Intermediate People's court said on a verified social media account on Friday.

The prosecution's case against Gao was reportedly connected to the 2013 leaking of an internal Communist Party communique calling for a harsh crackdown on dissent and warning against Western-style democracy and criticism of the ruling party's historical record.

Mo Shaoping, Gao's lawyer, said she 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.

One of Gao's lawyers, Shang Baojun, said Gao did not speak during the verdict and sentencing, but told her brother, Gao Wei, that she could not accept the result.

"We will definitely appeal," Shang said.

"We are very disappointed with this verdict," said Shang, who had argued in court that a "confession" from Gao had been extracted after threats were made against her son.

Verdict condemned

William Nee, a researcher for Britain-based Amnesty International, condemned the verdict, saying Gao is "the victim of vaguely worded and arbitrary state-secret laws that are used against activists as part of the authorities' attack on freedom of expression".

Gao went missing last April and resurfaced on China's state broadcaster a month later admitting she had made a "mistake" - a statement used as evidence by prosecutors at her trial.

Shang said the statement was made after police made threats against Gao's son.

He said that after the verdict was read out in court Gao had stated in a "strong voice" that she would appeal, but was not allowed to make any further statement.

China's definition of "state secrets" is notoriously broad, taking in the number of people executed each year, information about pollution, and databases listing commercial companies.

An outspoken advocate of liberal values, Gao was imprisoned following the government crackdown on student protests in Tiananmen Square in 1989.

She was detained with dozens of other government critics in the lead-up to the crackdown's 25th anniversary last year.

Gao's political writings saw her jailed for six years in the 1990s, also on a charge of "leaking state secrets".