Colombia's FARC rebels said Tuesday they have asked to meet with Pope Francis when he visits Cuba in September.

The guerrillas have been holding peace talks with a Colombian government delegation in Havana since November 2012. 

U.N. Secretary General Ban Ki-moon appointed a mediation expert Thursday as his representative to peace talks between leftist guerrilla fighters and the Colombian government.

Jean Arnault, who helped oversee implementation of the Guatemala peace process in the 1990s, will serve as delegate to the "Sub-Commission on End of Conflict Issues within the Colombian Peace Process," according to a U.N. statement.

Any peace deal to end Colombia's five-decade guerrilla war must include an amnesty for imprisoned FARC rebels, two of them told AFP in a rare interview from jail.

The issue is one of the most delicate at peace talks in Cuba between President Juan Manuel Santos's government and the Revolutionary Armed Forces of Colombia (FARC).

Fifteen police were killed Tuesday in Colombia when a helicopter taking part in an anti-drug trafficking operation crashed in a remote jungle-covered region, the national police force said.

A total of 17 officers were on board the Blackhawk helicopter, which was involved in an operation against the powerful Clan Usuga drug gang in northwestern Colombia's Antioquia department, said a police statement.

Colombia's Marxist FARC rebels, now negotiating a peace deal in Havana, said Sunday they hope to meet with Pope Francis on his upcoming Cuba visit.

Pope Francis will visit Cuba September 19 to 22 as part of a tour that will later take him to the United States.

A powerful earthquake with a magnitude of 6.1 rocked northern Colombia near its border with Panama on Tuesday, authorities said, though there were no immediate reports of injuries or damage.

The quake struck at 7:10 pm (0010 GMT Wednesday) at a depth of 30 kilometers (18 miles) in Choco department.

Colombia's FARC guerrillas on Tuesday praised President Juan Manuel Santos' decision to suspend air strikes against rebel forces, but urged further steps to de-escalate the half-century-old conflict.

Santos ordered the stand-down on Saturday, five days after the Revolutionary Armed Forces of Colombia, or FARC by its Spanish acronym, resumed a unilateral ceasefire.

Colombia's Nevado del Ruiz volcano erupted in an ash cloud on Sunday, prompting authorities to temporarily close two airports in the area.

The civil aeronautics agency said it closed airports at Manizales and Pereira as a precaution after the 8:30 am (1330 GMT) eruption.

Colombian President Juan Manuel Santos on Saturday ordered a halt to air strikes against the Marxist-inspired FARC rebels, giving a major boost to stop-start peace talks.

It comes just two days after the Colombian government and the FARC resumed talks following months of stagnation at the negotiating table and fighting on the battlefield.

Colombia and FARC rebels resumed peace talks Thursday with a new commitment to make progress after months of stagnation at the negotiating table and fighting on the battlefield.

The talks designed to end a 50-year-old conflict that includes Latin America's last and oldest insurgency have been dragging on since November 2012.