Luis Alfredo Garavito is said to have lured children to their deaths by offering them food and drink.

The BBC's Tony Smith: "Many of them were brutally killed and raped"

Colombia's chief prosecutor said most of Mr Garavito's victims were boys from poor families aged between eight and 16.

Alfonso Gomez Mendez said: "Luis Alfredo Garavito has admitted the murder of about 140 children.

"We have so far found 114 skeletons and we're still investigating the disappearance of other children."

He said the killer had struck across Colombia and that the authorities were now co-operating with police in neighbouring Ecuador, where Mr Garavito lived previously.

South America correspondent James Reynolds: "This tale of serial killing has shocked Colombians"

BBC South America correspondent James Reynolds said that Colombians, who are used to violence, have been shocked by the Garavito case.

If convicted, Mr Garavito will become Colombia's worst serial killer.

El Loco

Colombian police were first alerted to a possible serial killer in 1997 when they discovered the remains of 36 bodies in western city of Pereira.

Suspect: Luis Alfredo Garavito

Other bodies were found in at least 11 states.

Mr Gomez said: "Most had been found with throats slit, and signs of having been tied up and mutilated."

Many of the victims were children of street vendors who were often left unattended in parks and at traffic lights as their parents approached motorists.

Mr Garavito is said to have used a number of disguises to gain the children's trust, posing as a monk, a charity representative or a street vendor like their parents.

Mr Gomez said that the alleged killer often persuaded his child victims to walk with him to remote rural areas where he tied them up before torturing and killing them.

He said that in some of the towns Mr Garavito had travelled to, he became known as El Loco, meaning the crazy one, or El Cura, the priest.

Newspaper cuttings clue

The discovery of the mass grave, initially thought to be the work of a satanic cult, began the trail that led to Mr Garavito's arrest in April.

A nationwide task force was set up to investigate the killings and look for similarities with other cases across the country.

Mr Garavito was arrested in the eastern city of Villavicencio, where he was living under an assumed name, on suspicion of attempting to rape a 12-year-old boy.

A search of the apartments of a girlfriend and another friend found newspaper cuttings about several of the disappeared children, the prosecutor said.

Mr Garavito has been charged with the attempted rape but Mr Gomez said further investigations would be carried out before murder charges are brought.

He said Mr Garavito had confessed after being confronted with the evidence against him.