Jonathan Pollard, the American spy for Israel serving a life sentence in federal prison, was taken to the hospital and underwent surgery.

Pollard suffers from kidney and liver problems. He has been hospitalized several times in recent years. Haaretz reported Thursday that Effie Lahav, the head of the Committee to Free Pollard, told Israel’s Channel 2 that Pollard’s condition is “not good” and that “We are very concerned about his situation.”

There has been increasing clamor in Israel to free Pollard, a former Defense Department employee convicted of spying for Israel in 1985. One hundred of Israel’s 120 Knesset members signed a letter calling on President Obama to grant Pollard clemency, and in February 1,000 people demonstrated in front of the United States embassy in Tel Aviv, calling for his freedom.