Colombian President Juan Manuel Santos announced he was doing away with the hugely unpopular Departamento Administrativo de Seguridad after numerous instances of corruption and ties between its agents and right-wing militias blamed for killings.

The DAS was meant to operate on a brief similar to that of the FBI in the United States but in recent years it became deeply involved in violent factional politics that targeted left-wing politicians, journalists and citizens from other walks of life.

Colombia has been revamping its defense and security since Santos came to power in August 2010, buying defense and security equipment from international suppliers and refurbishing inventories, but his dissolution of DAS is the most radical step.

Santos quickly assigned some DAS responsibilities, handing domestic security and immigration tasks to the Interior and Foreign Affairs ministries, but he faces the challenge of rebuilding DAS departments that are still needed.

There was no immediate government comment on stopgap measures required to fill security holes left by the DAS dissolution.

The agency's formal responsibilities included investigating crimes against the internal security of the state, fraud against the state and its financial institutions, crimes affecting individual liberty and human rights.

DAS screened and maintained records on foreigners entering Colombia and for enforcing immigration laws. DAS had both investigative and intelligence-gathering and operated its own training schools in Bogota and Boyaca.

Many DAS operations were hugely controversial and drew criticism from the media and the opposition.

The dissolution leaves many questions unanswered and numerous security jobs still in the process of redistribution among other government departments.

In his speech announcing the dissolution, Santos said, "Today DAS turns 58 years old, and at 58 we are going to liquidate it."

"This is not a transformation, not a reform; the case of DAS is liquidation, DAS is done away with," he said.

DAS operations were marked by major scandals. In the most recent case to come to light, the Supreme Court sentenced a former DAS chief, Jorge Noguera, to 25 years in prison for his connections with paramilitary groups. The judges also fined Noguera $1.9 million.

The judges ruled that Noguera gave right-wing military groups details about labor union leaders, students and left-wing organizers who were then targeted for summary killings.

Noguera's conviction opened renewed controversy over the role played by Santos' predecessor former President Alvaro Uribe, alleged to have ordered wiretapping of both political allies and foes, judges and journalists.

Uribe has denied the accusations but critics cite his frequent reshuffles in DAS in response to past controversies over the agency's role in Colombian politics.