Colombia's Marxist FARC fighters have apologised for the "great pain" they caused by kidnapping thousands of people to finance half a century of conflict.

FARC, or the Revolutionary Armed Forces of Colombia, acknowledged in a video recording late on Sunday that it had taken captives over the years but would not do so again.

The fighters and government are gearing up to sign the accord after reaching agreement on August 24 to end a war that has killed more than 220,000 people and displaced millions.

About 7,000 FARC fighters will be incorporated into society and permitted to form a political party.

READ MORE: Colombia ceasefire ends half-century-long war

"We want to acknowledge, with the sentiment of humanity and reconciliation, that during the conflict the FARC also caused great pain with the retention of people for ransom," Ivan Marquez, FARC's commander and lead negotiator, said in the recording. 

"That conduct, while always used to sustain the needs of the rebellion, resulted in harming entire families."

Marquez was speaking from Havana, Cuba, where the negotiations took place.

Colombia ceasefire: Citizens to vote on peace agreement

About 27,000 people were kidnapped between 1970 and 2010, according official figures.

As many as 90 percent of those were seized by the FARC.

The two sides are scheduled to sign the peace agreement on September 26.

The deal will then be put to a vote in a plebiscite on October 2, allowing Colombians to decide whether to accept the accord.

Last week, the FARC's estimated 7,500 fighters started heading to collection points to give up their weapons under United Nations supervision.

Guerrillas who refuse to demobilise and disarm "will be pursued with all the strength of the state forces", Juan Manuel Santos, Colombia's president, told El Espectador newspaper.

Peace referendum

On October 2, Colombians will go to the polls to cast ballots in a referendum that Santos hopes will endorse the peace agreement.

"A victory for the 'Yes' vote will be a mandate from citizens for future governments," Santos was quoting as saying by El Espectador.

"The plebiscite will grant the political legitimacy that is needed."

Colombia: Talking peace with a FARC commander

The territorial and ideological conflict in Colombia has drawn in various left and right-wing armed groups and gangs.

It has left up to 260,000 dead, 45,000 missing and 6.9 million people uprooted from their homes.

Efforts to launch peace talks with another, smaller rebel group, the National Liberation Army, have yet to bear fruit.

Inside Story - Is the civil war finally over in Colombia?

Source: Al Jazeera News And Agencies