Colombians have demonstrated against the kidnapping of a nine-year-old boy who is the spokesman for a children's peace group.

Dagoberto Ospina was snatched a week ago by three heavily armed gunmen from a school bus in Cali, Colombia's second city.

According to other children on the bus, the kidnappers boarded the vehicle looking specifically for Dagoberto, checking school books for his name before taking him away.

The boy became known in Colombia last month, when he appeared on national television to plead for an end to the country's long civil war.

Children against violence

Dagoberto is a member of the group Builders for Peace, which has some 130 child members campaigning against violence in Colombia.

Soon after the kidnapping, his mother, Gloria Ospina, said she had known "something like this would happen".

Colombia has the world's highest incidence of kidnapping, with almost 3,000 cases registered last year.

Student demo

Political groups, students and celebrities have already staged protests against the kidnapping.

But the largest of all demonstrations is planned to take place in Cali on Thursday to demand Dagoberto's immediate release.

The city's schools will close and all students are being called to march in the main streets to protest against the kidnapping.

Several local and international NGOs and the Catholic Church will also take part.

It is still not clear who was responsible for Dagoberto's kidnapping.

The Colombian police say the crime could have been committed by National Liberation Army (ELN) rebels or by common criminals.

The country's main guerrilla group, the Revolutionary Armed Forces of Colombia (Farc), has denied any involvement in the incident.