37 civilians were killed and more than 60 wounded when gunmen ambushed a convoy transporting workers of Canadian gold miner Semafo in eastern Burkina Faso, regional authorities said on Wednesday.

The attack is the deadliest in recent years as the military struggles to contain Islamist violence that has overrun parts of Burkina Faso, located in western Africa. Semafo tightened security last year following armed incidents near two of its mines in the country.

The gold miner said in a statement earlier that the attack on a convoy of five buses with military escort took place on the road to its Boungou mine in the eastern region of Est, about 40 kilometers from Boungou, and that there were several fatalities and injuries.

The Est governor's office later gave more details, saying that "unidentified armed men laid an ambush for a convoy transporting Semafo workers," giving a provisional civilian death toll of 37 with over 60 wounded.

The toll does not include an unknown number of security forces personnel who may have been killed in the attack. The figure is likely to rise as there are a large number of people still unaccounted for, according to a security source.

Two security sources said the military vehicle leading the convoy was struck by an improvised explosive device on a stretch of road where there is no cellphone network.

Shortly after the initial explosion, an unknown number of gunmen opened fire. One of the sources said it appeared that they targeted the buses as well as the military escort, which was unusual.

In December a police vehicle was attacked on the same road, resulting in five deaths.

A Semafo spokeswoman said: "At this point, we do not have full information and are not in a position to add to this morning's release."

The Boungou mine is secure and operations are not affected, the company said.

(With input from Reuters)