The former head of the European Olympic Committee (EOC), Ireland's Patrick Hickey, has left prison in Rio de Janeiro vowing to clear his name as an investigation continues into charges he took part in a ring to illegally sell tickets to the Games.

A Rio court on Monday ordered the release of the 71-year-old, who was also the head of the Olympic Council of Ireland (OCI), but said he must remain in Brazil and had his passport taken away.

Hickey, who was released on Tuesday, had been held in Rio's Bangu 10 maximum security prison since his arrest on August 10 in a luxury beachfront hotel during the Games.

"I will now stay in Rio and my lawyers will proceed to have the charges laid against me set aside as there is no substantive proof of any wrong doing on my part," Hickey said in a statement.

The ticketing scheme, according to Rio police, allegedly involved the funnelling of Olympic tickets intended for use by the Irish committee and not authorised for resale to THG Sports, an international sports hospitality company.

Hickey has stepped aside from his Olympic positions during the investigation.

On Saturday, a court authorised the release of Kevin James Mallon, another Irishman and THG director, who was arrested days before Hickey and was being held in the same prison.

He left custody late on Saturday but is also not allowed to leave Brazil, his lawyer told Reuters.

Police have said they have ample evidence of crimes committed by both men and other suspects in the case, but a full investigation and further court proceedings to determine their guilt or innocence could take months.