At least 11 people were killed in three separate group killings in Colombia, police said Monday, one of the deadliest days since FARC guerrillas signed a peace accord with the government in 2016.

The massacres -- homicides of three or more people in the same event -- took place in the past three days in the regions of Antioquia in the northwest, Bolivar in the north and Cesar in the northeast of the country.

In a slaying Monday in Antioquia, five people were killed "presumably by an armed group" in the town of Zaragoza, Colonel Ever Gomez, the head of the region's police force, told reporters.

Also Monday, three men died in an attack in the area of Simiti, a town in the region of Bolivar. The victims had not immediately been identified, a police spokesperson told AFP. 

Police also reported that an attack occurred in the town of Aguachica, in the Cesar region. A Venezuelan couple were killed and a third victim died as a result of injuries sustained in the same incident. 

Experts warn that Colombia is undergoing a new cycle of violence that has been marked by an uptick in massacres just as the country hoped to have turned the page on the worst violence of the past, when left-wing FARC guerillas agreed to lay down arms in 2016 after decades of conflict.

Between January 1 and August 17, the United Nations recorded 33 such group killings in different regions of the country, compared to 36 in 2019, 29 in 2018 and 11 in 2017.

Since then, the authorities have recorded an additional 12 massacres. 

The government blames these acts of violence on armed groups that finance their operations through narco-trafficking. 

While the accord with the FARC -- which was the main guerilla group operating in the country -- reduced political violence, Colombia has lived for almost six decades with a conflict that has pitted state law enforcement agencies against guerillas, paramilitaries and narcotraffickers.