A blind activist leading a judicial campaign against forced abortions and sterilizations in China's eastern Shandong province has been confined to his home by authorities.

A senior official in Beijing promised Friday to investigate and punish local officials who break the law concerning family planning. The central government has been trying since the mid 1990s to move toward a system of fines and economic rewards to limit population growth, but many local officials continue to use forced abortions and sterilizations because their job performance is assessed on the basis of their success with family planning.

Chen Guangcheng, 34, who is preparing a class-action lawsuit challenging abuses of population control in Shandong, was detained in Beijing on Tuesday before he could meet with government officials who had expressed support for his cause. Local police transported him back to Shandong and let him go home the next day.

But in a hurried phone call on a cell phone Friday, Chen reported that authorities in his home town of Linyi, 400 miles southeast of Beijing, were preventing him from leaving his home or receiving visitors and had cut off his landline phone service. He said they had also seized his computer.

"I have no way to stay in touch with the outside world now. I think the situation is rather dangerous," he said, adding that officials had ordered all taxi drivers in the area not to take him anywhere and had installed lights around his house to better monitor him.

Chen said police had beaten him but had not charged him with any crime or provided any explanation for the restrictions on his movements. "This is basically an illegal detention," he said.

In an earlier interview, Chen's wife, Yuan Weijing, said a local official had warned her that her husband's life would be in danger if he didn't abandon the lawsuit. But Chen said he was determined to press ahead.

Chen has been collecting evidence from city residents who said local authorities had been requiring parents with two children to be sterilized and forcing women pregnant with a third child to have an abortion. Officials have also been detaining family members of parents who flee, beating them and holding them hostage until the parents return, residents said.

One of Chen's neighbors, Su Yongjun, said more than 100 police officers and local officials were posted in their village now to prevent Chen from leaving or receiving visitors.

An investigative team from the National Population and Family Planning Commission, the cabinet-level ministry responsible for managing population growth in China, visited Linyi last week but the members were unable to meet with Chen because he had left for Beijing.

In a written statement, Yu Xuejun, director-general of the commission's policy and legislation department, said the ministry "attached high attention" to the complaints in Linyi and had requested that the local government "consistently satisfy the requirements of rule of law throughout its family planning work."

"A thorough investigation takes time, to ensure that all parties concerned are treated in a fair and objective manner," he said. "The investigation is still not finished, but once it is, any infringements against the law that are proven to be factual will be punished."

China's state media have not reported on the alleged abuses in Linyi, but one official newspaper, the English-language China Daily, published an article Friday saying the government had launched an investigation into "serious human rights violations" in the city.