File photo - A Tunisian policeman. AFP
The guard "was wounded by a sharp object" wielded "by a person he was questioning over the reason for his presence in the perimeter of the embassy", the ministry said in a statement.
Security forces fired at the suspect, wounding him in the leg, before taking him into custody, the statement added, without indicating a motive for the attack.
Authorities have not identified the man, who was taken to hospital for treatment.
There was no immediate information on the guard's condition, but local media reported he too was hospitalised.
The North African country suffered a string of deadly jihadist attacks after its 2011 revolt which toppled dictator Zine El Abidine Ben Ali.
Tunisian authorities say they have made significant progress in the fight against violent extremist groups in recent years.
However, a deadly mass shooting hit the Tunisian resort island of Djerba last month.
The gunman, a police officer, killed three other officers and two Jewish worshippers, most of them outside a synagogue, before being shot dead himself by police.