
Mr Chen was taken to a Beijing hospital after leaving the US embassy
Chinese dissident Chen Guangcheng says he left his refuge in the US embassy in Beijing after Chinese authorities made death threats to family members.
Mr Chen was speaking from a hospital in the capital where he said he had agreed to come because of his fears for his family's safety.
The US said China had given assurances on Mr Chen's future and the agreement "reflected his choices and our values".
US Secretary of State Hillary Clinton is in Beijing for high-level talks.
Mr Chen had been at the US embassy for a week after escaping from house arrest in his home village in Shandong province.
The blind activist's case has threatened to overshadow the bilateral talks, which are due to focus on issues like Syria and trade.
Earlier Mr Chen's lawyer said the activist was "happy" after receiving "clear assurances" from Beijing.
But Associated Press quoted Mr Chen, 40, as saying he had been told by US officials of the threat from the Chinese authorities.
The agency quoted one US official as denying knowledge of the threat but the official did say Mr Chen was told his family would be returned to his home village in Shandong.
'Please help me'
The BBC's Michael Bristow in Beijing says both US and Chinese officials had said Mr Chen left the embassy his own volition but now a more complicated story is emerging.
A close friend of Mr Chen, Zeng Jinyan, herself an activist in Beijing, told the BBC she had spoken to Mr Chen and confirmed he had opted to stay in China to protect his family.
- Born 12 Nov 1971
- Nicknamed the 'Barefoot Lawyer'
- Went blind as a child
- Campaigned for women forced to have abortions or sterilisation under China's one child per family policy
- Jailed for four years in 2006 for disrupting traffic and damaging property
- Released from jail in 2010 placed under house arrest
- Daughter barred from school during much of 2011, reports say
- Escapes house arrest, April 2012
Ms Zeng said that Mr Chen "had no choice" because "thugs with sticks" were waiting for him and his family in their home village in Shandong.
She said: "It's impossible, he couldn't do anything. He said, 'please help me'."
Bob Fu, of Texas-based rights advocacy group ChinaAid, said reliable sources had also told it that Mr Chen had left the embassy because serious threats to his immediate family members were made by the Chinese government.
"We are deeply concerned about this sad development if the report about Chen's involuntary departure is true," Mr Fu said.
Hillary Clinton had earlier issued a statement saying: "I am pleased that we were able to facilitate Chen Guangcheng's stay and departure from the US embassy in a way that reflected his choices and our values.
"Mr Chen has a number of understandings with the Chinese government about his future, including the opportunity to pursue higher education in a safe environment," she said.
"Making these commitments a reality is the next crucial task. The United States government and the American people are committed to remaining engaged with Mr Chen and his family in the days, weeks, and years ahead."
But US-based China activist Yaxue Cao told the BBC she was angry at the US for reaching a deal with China.
She said: "If past indications are anything to go by, can you for a minute think China will guarantee Chen Guangcheng's safety. Is the State Department kidding?"
'Free citizen'
Mr Chen had been driven from the US embassy to a VIP section of Chaoyang Hospital for a check-up, before being united with his wife and two children.
He was reportedly accompanied to the hospital by US officials, but Mr Chen later told Britain's Channel 4 News: "Nobody from the [US] Embassy is here. I don't understand why. They promised to be here."

Security personnel kept journalists away at the Chaoyang Hospital in Beijing
Some 20 police officers ordered journalists to leave the hospital and detained one protester carrying a banner reading "Free Guangcheng. Democracy for China", Agence France-Presse news agency reported.
Earlier, Mr Chen's lawyer, Li Jinsong, said he had spoken to his client on the phone. He said Mr Chen was "very happy and wants to hug all his friends".
Mr Li said the dissident had told him he now had "true freedom", his rights were now protected by the national law and he was "a free citizen".
The affair has strained US-China relations at a delicate time.
Chinese foreign ministry spokesman Liu Weimin said: "What the US needs to do is to stop misleading the public and stop making every excuse to shift responsibility and conceal its own wrongdoing."
Mr Liu earlier said China was "strongly dissatisfied" and that the US should apologise.
Mr Chen had planned his escape for months, scaling the wall the authorities had built around his house and then being driven hundreds of miles to Beijing, where activists say he stayed in safe houses before fleeing to the embassy.
Several people involved in Mr Chen's escape have been detained or have disappeared in recent days.