More than 40 people who travelled hundreds of kilometres to visit blind Chinese lawyer-activist Chen Guangcheng amid a push to free him from house arrest were sent back by police, supporters said Sunday.

Chen is renowned for revealing forced sterilisations and late-term abortions affecting thousands of women in the eastern province of Shandong as part of measures to enforce China's population control policy.

The 44 supporters -- who come from all over the country but now live in Beijing to petition authorities for various grievances -- hired a bus and drove to Shandong on Saturday to see Chen on his 40th birthday.

They were blocked by police before they could get to his village and 13 were briefly detained before the entire group was driven back in a police convoy more than 500 kilometres (310 miles) to the northern city of Tianjin, near Beijing.

"We didn't get to see Chen Guangcheng, but we will try to see him again another time. We won't give up," Deng Zhibin, a petitioner who was part of the group, told AFP.

Activists organised through the Internet have been flocking to Chen's village in Linyi district as part of a growing online campaign to free the self-taught lawyer and rights campaigner, who has been blind since childhood.

But campaigners say thugs have beaten up many of those who were able to come close to the home of the lawyer, who has been under house arrest since he completed a four-year jail sentence last year.

Deng told AFP he and dozens of other petitioners had returned to Beijing and were now gathered near one of the city's railway stations to mark Chen's birthday with songs and banners -- a meeting likely to anger authorities.

"Dozens of us are singing happy birthday to Chen Guangcheng. We have birthday cakes and banners reading 'Rights Defenders from China celebrate Chen Guangcheng's birthday'," he said Sunday.

Foreign journalists who have tried to visit Chen since his release from prison have been roughed up or harassed and barred from gaining access to the village.

Chen himself and his wife Yuan Weijing have reportedly been severely beaten and threatened.