Iran releases 140 demonstrators

About 200 others, accused of more serious crimes, remain in the prison, BBC reported.

The release comes after Iran's supreme leader ordered the closure of another detention centre because it failed to "preserve the rights of detainees".

The unusual moves show how much pressure Iran's leaders are under over detainees, correspondents say.

But the BBC's Jon Leyne says the opposition will be sceptical of the change of heart - though there are many relatives of prisoners desperately anxious to be reunited with their loved ones.

Officials also announced on Tuesday that 30 people were killed in clashes between opposition supporters and police - up from a previously stated figure of about 20.

Speaking of the prison releases, National Security and Foreign Policy Committee member Kazem Jalali said those released had committed "lighter offences".

No well-known political figure was among the people released on Tuesday, he said.

The parliamentary committee is investigating the detentions.

The prisoner releases came after the committee visited the prison, Mr Jalali said.

Mr Jalali, quoted by Fars news agency, said 150 people who remain in prison were suspected of carrying weapons and bombs, and vandalising public property during the unrest.

A further 50 prisoners were described by judicial officials as the "agents of the unrest and some of them were members of anti-revolutionary groups".

These 200 cases were still being investigated, Mr Jalali said.

But one report suggests President Mahmoud Ahmadinejad has now ordered the swift release of all political detainees not facing serious charges.

"We want their families to be happy by their release," AFP news agency quoted him as saying in a letter to Ayatollah Mahmoud Hashemi Shahrudi, head of the country's judiciary.

"They should be home for the occasion of the birth anniversary of Imam Mahdi which falls on 7 August."

Supporters of the protesters say the true number of people detained may be in the thousands.