Colombian leftist rebels holding peace talks with the government insisted Wednesday that none of their people should end up in jail for fighting in the five-decade-old war.

That issue -- justice for egregious crimes committed during the war -- has proved to be a key stumbling block in the negotiations that began here in the Cuban capital in 2012.

Former leaders from Spain and Latin America called Monday on Venezuela's President Nicolas Maduro to free political prisoners, "respect fundamental rights and liberties" and create a climate for political dialogue.

The statement issued by 27 former leaders, followed Venezuela's refusal on Friday to grant two former presidents access to prisons holding opposition leaders Leopoldo Lopez and Daniel Ceballos.

Some 400,000 people in Colombia's bustling port city of Buenaventura lost power Sunday after a key electrical tower was destroyed -- an act military officials blamed on FARC rebels.

"At 9:45 am (1445 GMT) Buenaventura was left without electrical service," read a statement from the power company, the Energy Enterprise of the Pacific (EPSA).

Colombian soldiers killed two leftist rebels Saturday, the military said, amid renewed fighting that has shaken peace talks between the government and the FARC group.

The military said the latest clash occurred in the southwestern department of Narino, near the town of Tumaco.

The Colombian government and FARC guerrillas have begun clearing the country's landmines in a joint effort seen as a ray of hope in their stumbling peace negotiations, officials said Friday.

The pilot mine-clearing mission was carried out over seven days in the northern region of Antioquia, said officials from Cuba and Norway, the countries facilitating the talks.

A total of six soldiers and guerillas were killed in Colombia, as fresh fighting erupted between FARC rebels and government troops, authorities said Thursday.

Three soldiers were killed, and three Revolutionary Armed Forces of Colombia (FARC) rebels died in the clashes in northeast Colombia, in the oil-rich Arauca region near the border with Venezuela, according to a statement from the military, 

Colombian President Juan Manuel Santos on Wednesday warned his troops to stay prepared for conflict after leftist FARC rebels decided to drop their unilateral ceasefire.

The Colombian government and FARC negotiators resumed peace talks Monday in Havana amid heightened tensions following air strikes that killed dozens of rebels in Colombia.

The Colombian military killed at least five FARC guerrillas in the northwest of the country Monday, part of a new offensive that has challenged ongoing peace talks with the rebel group.

A bombing in the remote Choco department killed the fighters, military sources told AFP, but they were unable to provide more details about the attack.

Emergency workers have recovered the final bodies of people killed in a collapsed, unlicensed gold mine on an indigenous reservation in central Colombia, bringing the official toll to 15 dead, authorities said Monday.

"After 12 days of working around the clock... the bodies of the 15 miners who were trapped in the El Tunel gold mine when it was suddenly flooded... have now been recovered," said a statement from government disaster relief agency UNGRD, after the final two were brought out Monday.

The Colombian government and FARC guerrillas resumed peace talks Monday in Havana amid heightened tensions following air strikes that killed dozens of rebels.

Rebel leader Pablo Catatumbo condemned the government offensive as he arrived for the talks, which opened in November 2012 but have made only halting progress on ending the five-decade-old conflict.