The head of the World Council of Churches, the Rev Dr Samuel Kobia, has expressed his joy at Colombia's rescue on Wednesday of 15 rebel-held hostages, including politician Ingrid Betancourt and three Americans.

Former presidential candidate Betancourt, who holds dual French-Colombian citizenship, was held hostage by the left-wing insurgency group Revolutionary Armed Forces of Colombia (FARC) for more than six years.

Betancourt and 14 other hostages were rescued in a bloodless operation in the southern jungle province of Guaviare after Colombian soldiers tricked the captors into thinking they were aid workers before boarding the hostages onto a helicopter.

Dr Kobia said that the liberation was "an important step in a yet uncompleted process".

He called on FARC to release hundreds of remaining hostages "on a humanitarian basis", saying their continued detention was "an unacceptable situation which should be reverted immediately".

"Hostage taking should have no place in the processes of social and political transformation," said Kobia, before reiterating the call to President Alvaro Uribe and the FARC "to look for a peaceful solution of the conflict in Colombia".

Kobia urged mediators France, Switzerland, Spain, Ecuador and Venezuela to step up their efforts to "achieve peace with justice in Colombia".

Betancourt, 46, was kidnapped at a roadblock in FARC-controlled southern Colombia whilst campaigning for the presidency in 2002.

She said at a press conference following her release, "I feel like I am returning from a journey into the past."