OUAGADOUGOU- Dozens of people were feared still missing on Thursday after an ambush on workers near a Canadian-owned mine in Burkina Faso killed at least 37 and wounded 60 in the worst such attack in the West African nation for years.

Quebec-based gold miner Semafo SMF.TO said five of its buses with a military escort came under fire on the road leading to its Boungou mine in the eastern region of Est, about 40 kilometres (25 miles) from Boungou, on Wednesday. 

The assailants' identity was unclear, but Burkina Faso is struggling to combat surging Islamist violence in the remote eastern and northern scrubland areas.

It was unclear exactly how many people were in the convoy, what their nationalities were or how many were missing. But the company has said that under new safety guidelines, Burkinabe employees travel to and from the mine with a military escort by road while international staff are flown by helicopter.

Semafo had tightened security last year following attacks that killed three workers and five security officials.

Two separate sources who have worked at the mine said that the convoy left weekly carrying about 250 local staff usually in five buses of 50 to 60 people each.

Two security sources told Reuters that dozens may still be unaccounted for.

Government and military officials declined to comment.

A spokesperson for Canada's foreign ministry said there were no reports so far of any of its nationals being affected.

Once a pocket of relative calm in the Sahel region, Burkina has suffered a homegrown insurgency for the past three years, amplified by a spillover of jihadist violence and criminality from its chaotic northern neighbour Mali.

Wednesday's attack is the worst since jihadist groups with links to Islamic State and al Qaeda began targeting the landlocked nation with high profile attacks in January 2016.

Then, armed al Qaeda militants killed 32 people in a raid on a popular cafe and hotel in the capital Ouagadougou.

(Writing by Edward McAllister; Editing by Andrew Cawthorne) ((edward.mcallister@tr.com; +221 33 864 5782;))