Former Iranian President Mohammad Khatami, seen here at a pro-Mousavi rally in May, accused the ruling government on Wednesday of 'staging a velvet coup against the people and democracy.' (Hasan Sarbakhshian/Associated Press)

Former Iranian president Mohammad Khatami harshly criticized Iran's ruling regime on Wednesday and called for the release of people arrested in the aftermath of June 12's contentious presidential election.

Khatami, who was elected in 1997 and 2001, released a statement Wednesday accusing Iran's leadership of a "velvet coup against the people and democracy." He lashed out at what he termed "a poisonous security situation" in the wake of violent street protests.

"If you want to calm the atmosphere, why are you carrying out mass arrests? Oppressing people will not help end the protests," Khatami said.

"If these people have committed crimes, why are their legal rights as citizens not preserved; why don't they have access to a lawyer; why are they not tried in a court; why haven't they been charged?"

Khatami backed former prime minister Mir Hossein Mousavi in his failed presidential bid.

The results of the election showed incumbent president Mahmoud Ahmadinejad taking the vote over the challenger Mousavi by a 2 to 1 margin. Those results sparked widespread and often bloody protests across the country, as Mousavi and tens of thousands of supporters took to the streets, accusing the government of widespread fraud.

After ordering a partial recount, Iran's ruling clerics in the powerful Guardian Council declared the results of June 12 vote legitimate. The council called the election the "healthiest" vote since the 1979 Islamic Revolution and said there were only isolated instances of ballot inconsistencies.

Iran's Supreme Leader, Ayatollah Ali Khamenei, dismissed opposition calls for an annulment and has called on Mousavi and other reformist opposition leaders to stop protesting the vote's outcome.

Mousavi voices distrust

But Mousavi has refused to stay quiet.

In a lengthy statement Wednesday on his website, Mousavi said he considered Iran's cleric-led government illegitimate and demanded political prisoners be released, adding Iran's government needs to institute electoral reforms and ensure press freedoms.

"A majority of the people — including me — do not accept its political legitimacy," he said of the regime, adding: "There's a danger ahead. A ruling system which relied on people's trust for 30 years cannot replace this trust with security forces overnight."

In another development, the official tally of deaths among Iranian protesters during the street demonstrations following the vote was upped to 20 from 17 on Thursday, according to Iran's state-owned daily, quoting Iran's police chief Gen. Ismail Ahmadi Moghaddam.

Police detained 1,032 people, and most have been released, Ahmadi Moghaddam said, adding that 500 police were injured in the clashes. The report did not specify whether the numbers included those detained by the Basij militia, known as Khamenei's street enforcers.

Eight Basij members have also been reported killed in the street clashes.

With files from The Associated Press