"Our solidarity is with relatives of the victims of the plane crash of @COL_EJERCITO in Cundinamarca. Eight people lost their lives," Santos wrote on his Twitter account.
The crash occurred to the west of Bogota, between the towns of Facatativa and Zipacon, the governor for the region, Jorge Emilio Rey, said on his Twitter account.
The plane, a Cessna Caravan single-engine turboprop that can carry up to 14 passengers, was flying from the Guaymaral airbase in northern Bogota to Tolemaida, in a rural area southwest of the capital, the regional health secretariat said in a statement.
Rey issued a local declaration to facilitate emergency response efforts.
The army sent a team to investigate the cause of the crash.