BEIJING — The circumstances of a human rights lawyer's death at a Chinese military hospital have raised questions about the welfare of those who have defied the country's authorities.

Li Baiguang was a well-known lawyer who defended farmers and Christian pastors, work that garnered him an award from the Washington-based National Endowment for Democracy in 2008. He died on Monday just hours after being admitted to No. 81 People's Liberation Army Hospital in eastern Jiangsu province for a minor stomachache, a relative of Li's told Bob Fu, a religious activist who has known the lawyer for over a decade.

Fu said in a statement through his U.S.-based Christian nonprofit group China Aid that the "Chinese regime should be totally held accountable" for Li's sudden and "mysterious" death.

"The hospital alleged that he had liver problems and that he bled to death, but Li was previously healthy," the statement said. "China has a history of either neglecting the medical conditions of human rights activists until they succumb to them or declaring previously healthy people dead."

An employee surnamed Yang in the hospital's propaganda department said he had not heard of Li's case.

"I do not know who this person is," Yang said, adding that death and causes of death are a "private matter."

Earlier this month, Fu and Li had attended the National Prayer Breakfast in Washington together. Li's work defending arrested Chinese pastors often prompted death threats, Fu said.

The lawyer had been injured from an alleged beating by plainclothes security agents in October.

William Nee, a China researcher for Amnesty International, called for an urgent investigation to determine whether those injuries may have been a factor in his death.

"The government has the obligation to ensure that lawyers can carry out their professional duties without fear of intimidation or interference, and without being identified with their clients and causes," Nee said.

The National Endowment for Democracy called for an independent investigation into Li's death. The group noted Li had been "detained and physically attacked many times" for his work advocating for the rights of farmers and cited reports he had recently appeared to be in good health.

"It is essential that an independent and impartial investigation into Li's death be carried out before anyone accepts the official claim by Chinese authorities that Li Baiguang died from natural causes," said NED president Carl Gershman in the emailed statement.