Police in the Tunisian capital shot and wounded a man who tried to storm the Interior Ministry on Friday, local media and witnesses said.
Local Mosaique FM radio said police shot the man in the leg and brought him under control. He was taken to hospital, the radio said.
Witnesses said they saw police running after the man before shooting him.
"I am at the crime scene and I cannot give any details now," a ministry spokesman told Reuters.
In a post on their official Facebook page, police unions called the man an extremist and published pictures of a knife and cleaver that they said the man had carried.
A video posted on social media showed policemen shooting and pedestrians running on Habib Bourguiba Street.
Tunisian security forces have thwarted most militant plots in recent years and they have become more efficient at responding to those attacks that do occur, Western diplomats say.
The last major attacks in Tunisia took place in 2015 when militants killed scores of people in two separate assaults at a museum in Tunis and a beach resort in Sousse.