Anti-terrorism officials and prosecutors are investigating the tunnel.
Tunisian authorities have uncovered a tunnel near the home of the French ambassador during an anti-terrorism raid.
The underground tunnel had been dug from a Tunis house frequented by a known extremist, the Tunisian Interior Ministry said on Wednesday.
Authorities did not indicate the tunnel's purpose or whether the ambassador's residence was a target. Anti-terrorism officials and prosecutors were investigating further.
Security services were alerted after a tip-off about suspicious activity at the house in La Marsa, a coastal suburb of the Tunisian capital, where the French ambassador also lives.
An extremist known to intelligence services is among people who frequented the house, the ministry said in a Facebook post.
It did not say if there were any arrests were made during the raid that uncovered the tunneling.
The French Embassy in Tunisia has not yet commented on the matter.