The Security Council on Thursday tasked the UN mission in Colombia with monitoring a days-old ceasefire between the Bogota government and the country's last guerrilla group, the ELN.

Reached last month, the truce with the National Liberation Army went into force on Sunday, building on the historic peace deal with the FARC rebels, Colombia's oldest guerrilla group.

The council unanimously adopted a British-drafted resolution that welcomed the ceasefire and agreed to a request from the government for UN observers to take part in monitoring, alongside ELN representatives and the Catholic Church.

"We know that this is just the start," British Ambassador Matthew Rycroft told the council after the vote, who stressed that the top UN body had moved quickly to shore up the truce.

"Let us do all we can to support the government of Colombia and the ELN in that effort."

Under the measure, the mission will report regularly to the council on the ceasefire with the ELN, which is to remain in force until January 9.

The FARC and ELN were formed in 1964 to fight for land rights and to protect rural communities.

The conflict drew in leftist guerrillas, right-wing paramilitary groups and state forces and has left 260,000 people dead, more than 60,000 missing and seven million displaced.

After completing a first mission to oversee the disarming of FARC rebels, the United Nations in July established a second presence to help former combatants return to mainstream society.

The FARC has since launched a political party called the Common Alternative Revolutionary Force that will field candidates in next year's general elections.

Source: AFP