OUAGADOUGOU, Oct 4 (Reuters) - A large group of heavily armed militants killed 14 Burkina Faso soldiers and injured seven others in a dawn attack in the north on Monday, the government said in a statement. No group has claimed responsibility for the attack on the military detachment, which took place near the town of Yirgou, in the center-north Sanmatenga province, an area overrun by jihadist insurgents linked to al-Qaeda and Islamic State. Yirgou was the scene of another militant ambush in June, when at least 15 police officers were killed. Their unit had been visiting the town on a relief mission following a previous bout of militant violence. Attacks linked to al Qaeda and Islamic State have surged across Africa"s Sahel region, killing thousands and displacing millions across Burkina Faso, Mali and Niger. About 1.2 million people have been displaced by the violence in Burkina Faso alone.