Dzhamal had received little food or water, doctors say

Dzhamal Gamidov weighed only 15 kilograms (33 pounds) when police discovered him by chance.

The son of a Dagestan economy minister killed in a bombing in 1997, the boy was kidnapped in 2000.

Among those arrested for his abduction is head of the police department charged with fighting kidnapping.

There are frequent kidnappings in Dagestan, which borders the war-torn region of Chechnya.

'Horrible, horrible'

Dzhamal was discovered in the city of Khasavyurt on Wednesday, interior minister Adilgerey Magomedtagirov told Associated Press news agency.

"He was harassed, neglected," said Patimat Kabordiyeva, the head of the hospital intensive care unit treating the boy on Russian television.

"He had hardly received any food or any water."

The boy's grandmother told the station her grandson was "like a feather".

"It is horrible, horrible, but at least he is alive," she said.

Officials said the boy had been moved frequently from house to house throughout his ordeal. His captors had demanded a ransom of over $1m from the family.

'Famed rescuer'

Mr Magomedtagirov said they found the boy as police carried out a house-to-house search for the killers of a police officer.

His captors bundled him into a car and sped off in an attempt to evade the police, but eventually pushed him out as they drove.

Police caught them and made arrests, he said.

Among those arrested in connection with the case is Imamutdin Temirbulatov, the head of the regional kidnapping police unit.

Mr Temirbulatov was famed for rescuing kidnap victims, said AP.

He was fired from the Interior Ministry two years ago over differences with his department head, but had been reinstated on appeal.