In a statement, the organization said Ayatollah Qassim, who is in his 70s and has other health problems, including high blood pressure and diabetes, was “in continuous pain and excreting blood.”
The statement said the cleric’s family had implored the police surrounding his home to allow a visit on Sunday by doctors, who had recommended an emergency operation.
Sheikh Maytham al-Salman, a prominent interfaith cleric in Bahrain, said: “The Bahraini government holds the full responsibility of the Sheikh Isa Qassim’s well-being, as they imposed the house arrest and control his access to medical treatment.”
Responding to questions on Monday night, the Bahrain Embassy in Washington said the cleric’s family had rejected an offer of an ambulance to take him to the hospital.
“Sheikh Isa Qassim’s house arrest has no bearing on his access to healthcare, neither does his citizenship revocation,” the embassy said in an emailed statement.
Ayatollah Qassim’s worsening condition could incite unrest in Bahrain, an oil-rich kingdom that is closely aligned with Saudi Arabia and the United States and is home to the United States Navy’s Fifth Fleet. The fleet patrols the Persian Gulf and is a military counterweight to Iran, the region’s Shiite power.
Bahrain has been repeatedly roiled by protests among its Shiite majority since the Arab Spring uprisings of 2011. Bahrain’s police and security agencies, which have a reputation for using disproportionate force, have often crushed the protests violently.
Ayatollah Qassim has been an outspoken critic of the government’s tactics. He was punished in June 2016 by the Interior Ministry, which accused him of encouraging divisiveness and revoked his citizenship.
He is one of more than 480 people stripped of Bahraini citizenship since 2012, a punishment that Human Rights Watch has described as a tactic of political repression.
The cleric’s village, Duraz, has been under what human rights activists have called a continuous police blockade since the Interior Ministry’s order against him. The Bahrain Embassy statement said security measures were meant to increase public safety.
Last May, the cleric was given a one-year suspended sentence on charges of money laundering, which his supporters called a politically motivated, sham prosecution. Anger over how the cleric had been treated exploded in deadly protests outside his home.