* Map: tmsnrt.rs/34Dt463 (Adds quote from survivor's brother)
OUAGADOUGOU, Nov 7 (Reuters) - 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, the worst such attack for years in a nation plagued by jihadist violence.
Quebec-based gold miner Semafo 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.
Another 60 people were wounded, local authorities said.
The assailants' identity was unclear, but Burkina Faso is struggling to combat surging Islamist violence in remote eastern and northern scrubland areas of the West African state.
"Once more our people are in mourning because of terrorist groups that are multiplying, murderous actions against our civilians and our defence and security forces," President Roch Marc Kabore said in a televised address.
Semafo said the Boungou mine site remained secured, although it has suspended operations as a result of the attack.
It was unclear exactly how many people were in the convoy, what their nationalities were or how many were missing. But two security sources said dozens may still be unaccounted for.
One miner was shot in the leg but survived because the bodies of other victims fell on top of him, shielding him from the hail of bullets, his brother Benjamin Compaore said.
"There were more and more shots and then because the others were on top and he was underneath, God protected him," he said, speaking outside the Ouagadougou hospital where the wounded are being treated.
Semafo 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.
Two separate sources, who have worked at the mine, said the convoy left weekly carrying about 250 local staff, usually in five buses of 50-60 people each.
The company tightened security last year following attacks that killed three workers and five security officials.
A spokesperson for Canada's foreign ministry said there were no reports so far of any of its nationals being affected in Wednesday's attack.
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 was the worst since 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 and Alessandra Prentice; Editing by Andrew Cawthorne/Mark Heinrich