Fighters disguised as security officials have killed three Tunisian policemen and a civilian in an attack near the border with Algeria.
State news agency TAP said on Sunday that four gunmen dressed as Tunisian security officials killed the four and wounded two police and a border agent just after midnight.
The agency did not name any group in the attack, according to Reuters news agency. A statement from Tunisia's Interior Ministry said early on Sunday that fighters shot at a vehicle driving along a road in the northwest of the country near Jendouba, killing a prison official, a civilian and wounding two others, according to AP news agency.
The group then ambushed a patrol sent to investigate the attack, killing two members of the National Guard and wounding two others.
Tunisia's security forces have been battling fighters from the banned movement Ansar al-Sharia, whose leader has declared allegiance to al-Qaeda's North Africa wing.
The fighters stole weapons and a vehicle in d'Awled Manna, in northwest Jendouba province, TAP said.
Ansar al-Sharia was one of the most hardline groups to emerge after Tunisia's 2011 uprising against autocrat Zine el-Abidine Ben Ali, whose government often jailed opposition leaders.
Tunisia has continued its transition to democracy since the revolt, with a new constitution and elections scheduled for this year.
Earlier this month, police killed seven armed with suicide bomb vests and explosives in a raid north of the capital.
Ansar al-Sharia was blamed for storming the US embassy in Tunis in 2012.