After months of meetings to lay the groundwork for the talks, the government and the rebel group that calls itself the Central General Staff (EMC) announced they would hold official negotiations in Tibu, near the Venezuelan border.

The announcement, made in a press statement, did not say how long the ceasefire was meant to last, but local media said the parties had agreed on 10 months.

At the initiative of Colombia's first-ever leftist president, Gustavo Petro, the government wants to give the dissidents a second chance to lay down arms after rejecting a 2016 peace agreement with the FARC, of which they were then a part.

Petro took office last August with a vow to bring "total peace" to a country battered by decades of civil conflict between the state and various left-wing guerrilla groups, right-wing paramilitaries and drug traffickers.

The 2016 agreement saw about 7,000 members of the Revolutionary Armed Forces of Colombia (FARC) give up arms and attempt to reintegrate into civilian life, though a faction under guerrilla leader Ivan Mordisco decided to keep fighting.

The EMC steadily increased its presence in territories formerly occupied by the FARC and largely abandoned by government forces.

It is said by the government to be involved in cocaine trafficking, illegal mining and attacks on Colombian troops.

According to official data, the EMC had about 3,500 armed members by the end of last year.

At midnight on December 31, Petro announced a bilateral truce with Colombia's five main armed groups, but suspended the deal with the EMC in May after its fighters killed four Indigenous young men resisting recruitment.

This was followed by a military operation targeting the EMC in the Cauca department and others in the Amazon, where Mordisco and other leaders are thought to spend most of their time.

The EMC and the government started their latest round of talks in Colombia's southwestern Cauca region on Sunday, with delegates from the European Union, United Nations and the Organization of American States, among others.

Since last November, Petro's government has also held negotiations with the National Liberation Army (ELN) rebel group.