As many as 20 civilians have been killed in an overnight attack in north-western Burkina Faso.Unidentified heavily armed men on motorbikes carried out the attack on a village in Bani municipality, north of the capital Ouagadougou, on Saturday night, AFP news agency says.The attack comes a week after 39 people were killed when militants attacked a market in Silgadji town.The Sahel region has seen an increase in jihadist violence in recent months.News of Saturday's attack came as France announced it would send a further 600 soldiers to the Sahel region, bringing the total number of French troops to more than 5,000.Last year saw the highest death toll due to armed conflict in the region since 2012, with more than 4,000 people killed.The security crisis in the Sahel began when an alliance of separatist and Islamist militants took over northern Mali in 2012. France then launched a military intervention against them.Although a peace deal was signed in 2015, it was never fully implemented.New armed groups have since emerged and expanded to central Mali, Burkina Faso and Niger, including groups linked to al-Qaeda and the Islamic State group (IS).