The state of emergency has been in place since November 2015. It gives more power to police, especially to ban strikes and gatherings.
The decision comes after a police commander was stabbed to death by a suspected Islamic extremist near Tunisia's Parliament in Tunis earlier this month.
Tunisia suffered major extremist attacks in 2015, including at the famed Bardo Museum in the capital, where 22 people were killed. In addition, an attack on a beach hotel near Sousse killed 38 people and one on a bus carrying presidential guards in Tunis left 12 dead.
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