Iranian opposition leader Mir Hossein Mousavi has called on 17 political prisoners to end their hunger strike, citing concerns for their health.
The prisoners, said to include leading journalists and student activists, were jailed after last year's disputed poll.
Opposition websites say they are protesting against being held in solitary confinement, and being subject to humiliation in Tehran's Evin prison.
Four days ago, Mr Mousavi said five had been taken to hospital.
In the latest statement on his website, the opposition leader "praised the prisoners' steadfastness and resistance", but urged them to end their strike.
"Now that [your message] has reached the entire world and spread within the country, people are concerned about your health," he said.
The hunger strikers have been in jail since they were rounded up after the mass protests following the June 2009 vote, which saw President Mahmoud Ahmadinejad re-elected amid allegations of widespread fraud.
Thousands of protesters were detained in the wake of the demonstrations and some 200 activists remain behind bars. At least nine have been sentenced to death, and two have been executed already.
Several prisoners have reportedly embarked on hunger strikes with demands for immediate release, better treatment or access to lawyers.
Iranian film director Jafar Panahi was released on bail in May after three months in detention and several days on hunger strike.