By Agence France-Presse OUAGADOUGOU, Burkina Faso - Six policemen have been killed in an attack in northern Burkina Faso, in a region prone to jihadist violence, security sources said. A group of officers was ambushed on Monday "by armed individuals" in Soum province, one source said. Another source said the attack by "armed terrorist groups operating in the region" left six dead. It came after the government said 29 civilians were killed and six wounded in two attacks on Sunday in the northern province of Sanmatenga. The same day four soldiers were wounded in Yatenga province, also in the north, a security source said Monday. President Roch Marc Christian Kabore condemned, in a tweet, "these unspeakable attacks, these despicable acts (which) will not go unpunished". A former French colony that ranks among the world's poorest countries, the West African nation has been struggling with Islamist unrest since 2015. The country's army has been increasingly targeted by jihadists. Earlier this month, an attack on a military base in northern Burkina Faso killed 24 in an unprecedented blow to the army in its campaign against jihadists. The insurgency, which came from neighboring Mali, began in the north but has since spread to the east. Since 2015, more than 500 people have died in attacks that have become increasingly violent, according to a toll compiled by AFP. The capital Ouagadougou has been attacked three times, including a March 2018 jihadist assault on the military headquarters that left eight dead. A summit of regional heads of state is due to be held in Ouagadougou on Saturday to discuss the security situation.