An unidentified gunman killed three people in front of a Christian radio station in the Malian city of Timbuktu in a sign of renewed insecurity in the desert north.

Army spokesman Colonel Souleymane Maiga said on Friday the shooting took place in front of the Tahamint radio station late the previous evening. State radio said the three young men were seated for tea.

Security forces were searching for the gunman, Maiga said.

After a separatist rebellion in 2012,extremist militants with ties to Al-Qaeda seized the north, sending many residents, including much of the area’s Christian population, fleeing.

A French military operation recouped control of main towns the following year but violence has intermittently flared and extremists have struck out beyond the region, including killing 20 people in November at a luxury hotel in Mali’s capital.

The United Nations’ senior official in Mali announced on Thursday he would be leaving his post amid difficulties with security improvements in the north and issues implementing a peace deal signed in June.