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Ten police officers have been arrested in Colombia on suspicion of involvement in the killing of three youths.

The three were shot dead while in police custody in northern Sucre province on 25 July.

A police colonel, the highest-ranking officer suspected in the case, is on the run and thought to be abroad.

Prosecutors say the police officers had alleged that the youths were members of the Gulf Clan criminal group that had earlier shot dead a policeman.

Colombia has a dark history of "false positives" - cases in which civilians were murdered by the military and passed off as rebels to boost its kill rate.

An inquiry found last year that Colombia's military killed more than 6,400 people between 2002 and 2008 and falsely labelled them as enemy combatants.

While the majority of "false positives" occurred during the height of Colombia's armed conflict with left-wing rebels - and were carried out by the military rather than the police - the case of the three youths has caused alarm.

The outgoing head of the country's police force, General Jorge Luis Vargas, said that any officer found to be responsible would face the full weight of the law.

Gen Vargas also ordered that the police commander in Sucre province be suspended.

The three youths were detained shortly after a 25-year-old police officer, Diego Ruiz, was shot dead in a bakery by armed men suspected to belong to the Gulf Clan.

During the search for the gunmen, police detained Jesús Díaz, José Arévalo and Carlos Ibáñez and took them away in a van.

Eyewitnesses said the three were alive when they were put into the back of the van but a short time later, when police took them to hospital in the same van, doctors declared them dead on arrival.

Medical reports suggest their bodies had sustained multiple bullet wounds.

Relatives of the youths, who were between 18 and 26 years old, said that the three had no connection to the Gulf Clan.

Colombia's new chief of police, General Henry Sanabria, said an Interpol red notice had been issued for the arrest of Colonel Núñez, who he said was the main suspect in the shooting.

Colonel Núñez left Colombia the day after the shooting and is thought to be in Mexico.