Algeria arrested former Tunisian intelligence chief Lazhar Longo and handed him over to Tunisia after he turned up in the neighboring country, a Tunisian security official told Reuters on Thursday.
He was reportedly arrested while trying to illegally cross the border between the two countries.
Observers believe his arrest is a result of security coordination between Algiers and Tunis.
Algeria did not immediately comment on the arrest.
A controversial figure, Longo, who also served as a Tunisian security attaché in Paris, was sacked and placed under house arrest last year after President Kais Saied seized control of executive power and closed the parliament.
Longo is close to former Tunisian Prime Minister Hichem al-Mechichi and the moderate Islamist Ennahda movement.
