A man wearing a balaclava tried to force his car through the gates of a military base in Belgium on Monday, but prosecutors said there were no signs of a terrorist motive.
Prosecutors said they did not rule out that he was mentally unstable.
The man tried to enter the barracks in Flawinne, near the city of Namur and fled when soldiers opened fire on his car, prosecutors said. No one was hurt.
The suspect, identified only as a man born in 1983, was later detained and found to be unarmed. There were no explosives to be found in the car.
"For the moment there are no elements which would allow us to say we are facing a terrorist examination," Namur prosecutor Vincent Macq told a press conference.
"The theory of an isolated incident or one of a psychologically unstable person cannot be ruled out," he added.
Belgium foiled what authorities say was a plot to attack police in January, killing two men in one of several raids against an Islamist group that officials said had been about to launch large-scale attacks.
Since then, soldiers have been guarding several sites across the country, such as the European Commission headquarters, embassies and Jewish schools in the capital Brussels.