Blind Chinese activist Chen Guangcheng told AFP Friday he was in "great danger", and urged the Chinese government to respect commitments it made about his safety when he left the US embassy.
"I am in great danger.... I hope the government will respect the commitments to guarantee my rights agreed to between China and the United States," he told AFP in a telephone interview.
Chen said he never raised a request for political asylum with the US government, but expressed worries that security personnel at his Beijing hospital were preventing US embassy officials from meeting him.
"They don't let the (US) embassy staff come in. I think there are some big problems," Chen said.
"I haven't seen them since the day before yesterday (Wednesday)."
Chen fled his home in the eastern province of Shandong on April 22, and later recorded a video appeal to Premier Wen Jiabao in which he said he and his family had been subjected to repeated abuses at the hands of local authorities.
He sought refuge at the US embassy, but on Wednesday US officials announced he had left the embassy for a hospital to receive treatment and be reunited with his family.
US officials said China agreed to guarantee the safety of the activist and allow him to attend university.
Chen was jailed in 2006 after exposing forced abortions and sterilisations linked to China's draconian "one child" population control policy and has been under strict house arrest since his prison release in 2010.
Since entering the hospital, one Chinese official has visited him and discussed his situation, Chen said.
"It was an official from the petition bureau (handling complaints from the general public). It is not useful to talk about this. My situation is very, very critical," he said.
Chen further expressed concerns over police beatings of supporters who had come to try to visit him at the hospital.