A member of the Revolutionary Armed Forces of Colombia (FARC) delegation attending peace talks in Havana said the group had no involvement in Wednesday's bombing in the town of Quibdo, which also injured 10.
FARC negotiator Marcos Calarca said the group was habitually accused of violence by authorities in Colombia.
"We are used to this. Everything negative that happens in Colombia is attributed to the FARC," Calarca said. "Even if crops are damaged by heavy rain or drought it is our fault."
Local police in Quibdo, the capital of Choco province on the border with Panama, had earlier blamed the FARC for the attack.
Police in Quibdo also are investigating the possible involvement of another armed group, los Urabenos.
That group, made up of former rightwing paramilitaries, is one of Colombia's most feared drug-trafficking organisations.
