Colombia's Farc rebel group has released eight of the 10 hostages it kidnapped last week, the International Committee of the Red Cross has said.

The hostages were abducted from a boat travelling along the River Atrato in the western province of Choco.

Two have been retained and authorities believe a ransom will soon be demanded.

It is the first release of hostages by the Farc since the military rescued 15 high-profile hostages earlier this month, among them Ingrid Betancourt.

It is also the first major operation involving the Red Cross in Colombia since the organisation criticised the government for allowing the use of its emblem to help trick the rebels into handing over their captives.

The BBC's Jeremy McDermott in Bogota says the release of the hostages to the Red Cross suggests the Farc has not lost faith in the humanitarian organisation.

"The operation was made possible through discreet dialogue between the parties concerned," said Yves Heller, an ICRC spokesman in Colombia. "We continue to work as a neutral mediator."

The left-wing Farc has waged a 44-year civil war in Colombia and still holds 700 hostages.