Blind activist Chen Guangcheng said Thursday China had agreed to issue him a passport within 15 days, allowing him to go to the United States after a bitter row between Beijing and Washington.

It was the first indication of when Chen would be allowed to leave the country since he left the US embassy more than two weeks ago after seeking refuge there following his dramatic escape from house arrest.

Speaking to AFP by telephone from the hospital where he is being treated, Chen also said authorities had promised to investigate murder charges brought against his nephew that he has said are motivated by revenge.

"Officials visited yesterday, we filled out passport application forms for myself, my wife and children," said the 40-year-old legal campaigner, who triggered a diplomatic crisis when he fled to the US embassy last month.

"They said the passports should be issued within 15 days," he added. The couple have a nine-year-old son and a six-year-old daughter.

Chen, one of China's best-known dissidents, has won plaudits for exposing rights abuses including forced sterilisations and late-term abortions under China's "one-child" family planning policy.

His activism earned him a four-year prison sentence that ended in 2010 when he was placed under extra-judicial house arrest in his home village of Dongshigu in the eastern province of Shandong, where he languished until his escape.

Wednesday's meeting with government officials was his first since May 7, when they told Chen they were processing papers for him to leave for the US, where he has been offered fellowships to study law.

Details of his dramatic flight from house arrest have gradually emerged during his time in hospital, and on Thursday, he told how he feared for his life and for the safety of the villagers who helped him.

"After I escaped from home, that is when I was the most worried," Chen said.

"There were at least 60 or so people guarding me in the village. If they had discovered I had escaped they could have beaten me to death. At that time it was very, very dangerous."

News of Chen's escape broke just days before US Secretary of State Hillary Clinton arrived in Beijing for pre-arranged talks and made headlines around the world, causing major embarrassment for the Chinese government.

As Clinton arrived in China, Chen left the US embassy and was taken by diplomats to a Beijing hospital after Chinese authorities guaranteed his safety.

Since then, he has accused local officials in Shandong of targeting his relatives out of revenge for his escape.

His nephew, Chen Kegui, is in detention charged with "intentional homicide" over an attack on a local official who broke into the family's home after discovering that Chen had escaped from under the noses of his guards.

The official was said at the time to have survived the attack and the charge has baffled lawyers representing Chen Kegui, who say it will not stand up in court. Police in Yinan county, which includes Dongshigu, refused to comment on the case when contacted by AFP.

Chinese Human Rights Defenders, a rights group, said police had detained and tortured Chen Guangcheng's older brother Chen Guangfu, the father of Chen Kegui, on April 27 -- the day of the break-in.

"Authorities handcuffed Chen Guangfu and shackled his legs, and then whipped his hands with a leather belt, struck him in the ribs, and stomped hard on his feet," the group said in a statement late Wednesday.

"The abuses against Chen Guangfu represent the most physically violent treatment to surface so far among the spate of retaliatory acts towards those with links to Chen Guangcheng after his flight from house arrest."

Chen Guangfu remains "under strict control" and cannot contact other family members, including many who are also being monitored by authorities, the group said, citing local sources in Yinan.

Chen Guangcheng said the government officials who visited him on Wednesday had promised to investigate the situation.

Two lawyers had tried to visit Chen Kegui on Wednesday but were turned away by police.

"Yinan police said the person in charge was not there and did not allow them to see Chen Kegui," Chen Guangcheng told AFP, adding he feared authorities were refusing visits because his nephew had been beaten.