Some 250 people have held a rally in support of Akbar Ganji, the jailed Iranian dissident writer who has now been on hunger strike for 63 days.
Supporters and friends of the writer fear for Akbar Ganji's life
Ganji's supporters - including many well-known reformers - were trying to persuade him to resume eating.
They gathered in front of the Tehran hospital where he is being held, singing and waving banners.
Ganji started his hunger strike in June to pressure judges to grant him unconditional release.
Ganji, who is said to have lost 30kg (66lb) is reportedly in intensive care.
He was jailed in 2000 for "acting against national security" and other crimes, after linking top officials to several political murders.
"We call on Akbar Ganji to halt his hunger strike and urge the authorities to free him in accordance with the law," his supporters said in a statement.
Student leader Ali Afshari told Reuters news agency officials at the hospital had prevented a delegation from visiting the writer.
"From now on, the responsibility for Akbar Ganji's life rests on the shoulders of those who didn't let us in," he said.
The European Union has urged Iran to release Ganji on humanitarian grounds, but Tehran dismissed the request as illegal.
Last week Ganji's wife, Massoumeh Shafeih, begged friends and supporters to persuade him to end the hunger strike.