LA PAZ - Bolivian President Evo Morales demanded on Monday a "thorough investigation" into the killing of Deputy Interior Minister Rodolfo Illanes and three miners last week.

"We mourn the fallen brothers. There has to be a thorough investigation and come what may, they have to be prosecuted," said Morales during a ceremony with the unionized miners from Colquiri held at the presidential palace.

Bolivian police have arrested 10 miners and are searching for 12 other people implicated in the murder of Illanes, who was sent last Thursday to have a dialogue with protesting miners, but was kidnapped and tortured.

The Public Prosecutor's Office said suspects are largely leaders of the unions who issued threats at the scene. Police had released some 40 protesters arrested earlier over Illanes' death.

According to officials, some 100 miners "forced him to climb a hill on his knees" until his bones were fractured "before stoning him to death." Meanwhile, the miners laid a trap with explosives in case police arrived.

Illanes' death led to an end Friday of weeks of violent protests in which miners had blocked a highway and clashed with police for more union rights and more mining concessions from the government.

Bolivia's energy sector is nationalized. Protesters' demands included freedom to sign contracts with private mining firms and a free supply of electricity.

On Monday, Morales said that in the past weeks "we experienced very difficult moments in Bolivia".

"There is no point abusing our trade union strength. There is no point abusing the social force in any sector, you need to be careful of this as it is the heritage of the workers," he noted.

The president, who said Saturday the protesters showed a "clear intent" to destabilize the government, said he regretted that some sectors wanted to "take advantage of" the government intention for dialogue, trying to pressure the government into meeting their demands.