(Adds Maduro comment, paragraphs 11-13)
By Diego Ore
CARACAS, May 27 (Reuters) - An imprisoned former Caracas police commissioner at the center of stalled political talks between Venezuela's government and opposition went on a hunger strike on Tuesday, demanding he be released due to frail health.
Ivan Simonovis, 54, was sentenced to 30 years behind bars after being convicted of participating in the assassination of four protesters during a march that triggered a brief coup against the late President Hugo Chavez in 2002.
Freedom for Simonovis has become a rallying cry for the opposition, which has expressed outrage at his imprisonment in a small cell and says his osteoporosis requires urgent medical attention.
The issue was a factor in this month's collapse of negotiations between the opposition and President Nicolas Maduro's government. The talks had been aimed at ending street protests that had been raging since February.
Protesters staged near-daily marches over three months to decry crime, inflation and food shortages. It was the worst unrest since a tumultuous two-year period around the time of the coup.
The demonstrations have ebbed in recent weeks but Simonovis' announcement may rekindle passions in deeply polarized Venezuela.
"All the legal and political efforts to receive a response to the (release) demands I made 10 months ago have been exhausted," Simonovis said in a letter read by his lawyer in front of the Supreme Court.
"I'm tired of acting in accordance to the law, yet no one listens to me. Despite my health condition and against the will of my family, I've decided to start a hunger strike in my cell as of today," the letter said.
Simonovis is one of the highest-profile cases among several dozen opposition-linked figures who ended up in prison during Chavez's 14-year rule from 1999.
For government supporters, Simonovis is a dangerous and violent saboteur who played a role in illegally unseating a democratically elected president. He was sentenced in 2009 after lengthy proceedings. Several other officers were convicted.
Later on Tuesday, Maduro slammed mainstream media for seeking to "convert a murderer into a victim."
"I won't waver in ensuring justice is done," he said during an hours-long radio program called "In Contact with Maduro."
"One sees that there's not even a minimum of reflection, of regret here. To the contrary, (opponents) continue to seek the same thing, to use violence to impose a capitalist, retrograde and repressive regime in Venezuela."
In recent months, the government has arrested more than 3,200 people during protests, of whom 224 remain behind bars, according to government figures. The best known is Leopoldo Lopez, a hardline opposition leader.
Senior Socialist Party official Jorge Rodriguez infuriated Simonovis's supporters earlier this month, saying the man's case was not on the agenda of the now-suspended talks despite opposition assertions his release was being negotiated.
"Those were vivid fantasies," Rodriguez said.
Simonovis's family say his health is so weak he runs the risk of breaking bones from simple acts such as lacing up his shoes.
The case may evoke memories of farmer Franklin Brito, who died in 2010 after a hunger strike to protest against Chavez's land takeovers. (Writing and additional reporting by Alexandra Ulmer; Editing by Andrew Cawthorne, Jonathan Oatis and Paul Tait)