Gunmen killed five people in southern Colombia on the border with Ecuador, authorities said on Wednesday.
Attackers on motorbikes opened fire indiscriminately at a group of eight people on Tuesday night, said Putumayo department police chief colonel Jorge Salinas.
Five people died at the scene and the other three, including two women, were injured, Salinas told a local radio station.
The area of the attack was known to be frequented by drug addicts.
Police suspect a faction of dissidents of the Revolutionary Armed Forces of Colombia (FARC) rebels called the Border Commandos to be behind the attack.
Marxist FARC guerrillas signed a peace treaty with the government in December 2016 to end a half centry of conflict with the state and create a communist political party.
But some dissidents refused to lay down their arms and continue to carry out attacks on the armed forces and civilians, while mostly funding their campaign through drug trafficking.
The Border Commandos were involved in a clash with another group of FARC dissidents in Putumayo a month ago, in which at least 20 suspected fighters died.
Armed groups throughout the country are fighting over territory and the lucrative drug trafficking trade.
Colombia is the world's largest producer of cocaine, much of which is shipped out of Ecuador to the United States -- the number one market -- and Europe.
Following the murders, Colombia President Gustavo Petro and his Ecuadoran counterpart Guillermo Lasso proposed joint operations along the shared 586-kilometer (364-mile) long border in a Twitter exchange.
Petro said these operations would target the "mafias that use the border as a drug trafficking route."
Lasso replied that he could "count on our active support."
Petro, who is Colombia's first leftist president, has vowed to negotiate with armed groups and drug traffickers in a bid to achieve a "total peace" in a country that has now suffered almost six decades of conflict.
Initial talks with these groups, including the rebel National Liberation Army, or ELN, have not so far resulted in a reduction in violence.
On Wednesday the ELN announced it was launching an "armed strike" in a poor region of northeastern Colombia beginning Thursday evening.
The rise in tensions comes at a poor time for Petro's government, which had announced early this week it had successfully concluded a first round of negotiations with the guerrillas -- although no formal ceasefire was reached.
Colombian officials say the ELN currently has some 2,500 members and is mainly present in the Pacific region and along the 2,200-kilometre border with Venezuela.
According to the Indepaz NGO, there have been 93 massacres this year in Colombia, leaving scores of victims.
