Suspected Islamist militants killed two civilians and a customs officer and burned a car in an attack on a customs post in Mopti, central Mali, on Thursday, a defense ministry spokesman said.
Islamist militants based in the north of the country have expanded their range in recent months with a series of raids.
Militants killed 20 people in a high-profile raid on a hotel in Mali's capital in November and 30 more in an attack in the capital of Burkina Faso last month.
On Tuesday, a military vehicle hit a land mine in central Mali, killing three soldiers, a defense ministry statement said.
The most active group is al Qaeda in the Islamic Maghreb, but the Macina Liberation Front, whose leader is Amadou Kouffa, is suspected over the Mopti attack, a security source said.
Islamist militants held towns in northern Mali in 2012 until French forces drove them out a year later but an operation led by French forces since then and a U.N. peacekeeping mission has failed to stop the attacks.