A YOUNG French man who was recently discharged from a psychiatric hospital is under investigation for glorifying terrorism after he brandished a knife and tried to breach security at the Eiffel Tower.

No one was hurt in the incident late on Saturday although the tower was briefly evacuated. The tower reopened as usual on Sunday morning.

A judicial official said the man tried to force his way into the secure zone, held out a knife and said "Allahu akbar," the Arabic phrase for "God is great".

He was quickly surrounded by security forces and surrendered, the official said. A Paris police official said no shots were fired.

While the man is accused of glorifying terrorism, the incident is being investigated as a common crime and not by anti-terrorism investigators, the judicial official said, because of his history of psychiatric problems and because authorities have no reason to believe he was part of a network or planning an attack.

The suspect was born in Mauritania in 1998 but has French citizenship, the official said.

Monuments in the French capital are occasionally evacuated for security reasons, as the country remains on alert after deadly attacks since 2015.