A group of police officers and oilfield workers taken hostage during protests in Colombia's southern Caquetá province have been freed, President Petro says.

Violence erupted on Thursday after residents blockaded an oil exploration company's compound. They were demanding its help to build roads in the area.

Colombian leader Gustavo Petro had called for the 79 officers and nine Emerald Energy employees to be let go.

A police officer and a civilian have already been killed during the unrest.

Announcing the release of the hostages, who were filmed sitting in a crowded room on the floor, Mr. Petro called on investigators to find those responsible for the two deaths.

Interior Minister Alfonso Prada said earlier on Friday that they were killed by gunfire.

Many of the protesters are rural and indigenous people who want Emerald Energy to build new road infrastructure around the San Vicente del Caguan area.

The oil company did not respond when approached by Reuters news agency for comment.

Colombian police paid tribute on Twitter to the police officer killed in the clash, who they named as Ricardo Monroy.

“Today we are more united than ever,” they wrote, adding that Mr. Monroy had “offered his life in the line of duty”.

Colombia's human rights ombudsman Carlos Camargo - who was on site to mediate - said he had spoken to protesters and stopped them from throwing petrol bombs at the oil facility.

Protests in areas near energy and mining operations in Colombia are common as communities demand companies build infrastructure, including roads and schools.

Police said a dissident subgroup of Farc rebels which rejected the 2016 peace deal were present in the region and may have been provoking the unrest.

Separately, Mr. Petro on Thursday unexpectedly published a statement on Twitter asking the country's prosecutor general to conduct a criminal investigation into allegations of corruption involving his own son and brother.

The statement did not specify the accusations against his eldest son, Nicolas Petro Burgos, and brother, Juan Fernando Petro Urrego, but it did say: “my government will not give out benefits to criminals in exchange for bribes”. (BBC)

Police held hostage in Colombia protest

•PHOTO:A group of police officers and oilfield workers taken hostage during protests in Colombia's southern Caquetá province have been freed.