The Colombian rebel movement FARC said Thursday that 11 lawmakers it was holding hostage were killed during an attempt to free them this month.

The 11 local deputies "were killed in the crossfire" on June 18 during an attack on the camp where they were being held, said a statement published by ANNCOL, a news agency close to the guerrillas.

The Colombian military promptly denied ordering an operation to free the hostages, in a statement from army commander Freddy Padilla.

The dead were among a group of more than 50 hostages held since 2002 by the Revolutionary Armed Forces of Colombia (FARC) since 2002. Those held also include another deputy, three Americans and the French-Colombian politician Ingrid Betancourt.

The Marxist group -- the biggest rebel movement in Colombia with some 17,000 members -- has been demanding the release of 500 of its own members detained by the government in return for freeing the hostages.

"To the families of the deputies who were killed, we express our deep regret for this tragedy," the FARC said in the statement, adding that it would return the bodies as soon as possible.

It said the other lawmaker survived because he was not in the camp at the time.

Former prisoners of the FARC have said that the guerrillas are instructed to kill their hostages if the military tries to free them.

Eight soldiers and two former officials also died in a failed rescue attempt in May 2003.

The group also criticized what it termed the "intransigence" of Colombia's President Alvaro Uribe, accusing him of pushing to free the hostages by force.

Uribe earlier this month released 150 jailed FARC rebels, including one of its leaders, Rodrigo Granda, hoping for a reciprocal release by FARC of some of its high-profile hostages.

Granda's release came at the request of French President Nicolas Sarkozy, who is concerned about French-Colombian politician Ingrid Betancourt. She was kidnapped in 2002 while running for president.