Xi Wenli, Qin Yongmin and Wang Youcai were jailed for 13, 12 and 11 years respectively after short, closed trials.

A Chinese Foreign Ministry spokesman said the proceedings had been fair and open.

Activists have protested against Mr Qin's trial

Responding to criticism by Western governments of both the trials and the sentences he said such criticisms were irresponsible and unacceptable.

China, he added, did not interfere with the judicial affairs of other countries.

Qin Yongmin was found guilty of subversion for his links with the recently formed China Democracy Party (CDP).

He was also stripped of his civil rights for three years by the court in the central city of Wuhan.

There has been international condemnation of his conviction and that of two other CDP founders.

BBC Beijing Correspondent Carrie Gracie says China's Communist authorities have clearly decided to make an example of the three most prominent figures involved in setting up the party.

BBC Beijing Correspondent Carrie Gracie: Xu Wenli tried to exercise rights supposedly in the Chinese constitution

Britain, France, Germany and the United States denounced the crackdown.

The hefty punishments come just 10 weeks after China signed the UN International Covenant on Civil and Political Rights, which guarantees free speech and assembly.

Washington said the sentencings were deplorable and called on the Chinese authorities to release the men immediately.

US-based Human Rights Watch said China's "summary trials" made a mockery of its international commitments.

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About 200 activists have signed a petition calling for the men's release.

But the Chinese authorities have warned they will continue to take a tough line against dissent.

Our correspondent says the trials have gravely damaged the reputation China was trying to build for a more free and open judicial system.

Observers were kept away, attempts to mount a defence were obstructed and the court hearings lasted only a matter of hours.

Heavy security

Mr Qin, 45, had tried to set up an independent human rights monitoring group in addition to organising the CDP.

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His brother said Mr Qin's trial lasted just half a day and officials refused to let him into the courtroom for the sentencing.

Mr Wang, 32, who was a student leader in the 1989 Tiananmen Square demonstrations, was sentenced after a trial in the eastern city of Hangzhou.

Mr Xu, 55, a veteran campaigner, was detained last month after setting up a CDP branch in the Chinese capital.

Journalists were prevented from entering his trial at a Beijing courthouse which was ringed with heavy security.

Mr Xu's lawyer said he refused to defend himself against the charges, which he said stemmed from political persecution.

His wife said he told the court: ''I'm willing to use the sacrifice of myself to promote democracy in China.''

Mr Xu edited an influential dissident journal in the Democracy Wall movement 20 years ago and spent 12 years in prison, most of them in solitary confinement.

In the last two years the Communist Party has relaxed some controls on dissenting views among academics.

Activists had seen the more open atmosphere as an opportunity to form a democratic party.

In the last six months they had tried to set up branches of the CDP in 14 provinces and cities.

The sentences came after another dissident, Liu Nianchun, was freed from a labour camp and flown to exile in the US at the weekend.