(Reuters) -- Tunisia has been on high alert since 2015, when Isis gunmen killed dozens of foreign tourists in a museum in the capital, Tunis, and on a beach in the resort city of Sousse.

Algerian Bilel Kobi was "the right arm of Abou Wadoud" and was killed in an ambush near the Algerian border when on a mission to reorganize AQIM's Tunisian branch following strikes by Tunisian forces against it, the source told Reuters.

Last year Tunisian forces killed extremist militants including Mourad Chaieb, the Algerian leader of Okba Ibn Nafaa, a group that has fought for years with security forces in Tunisia's mountainous interior.

The country also faces a potential threat from Tunisian militants returning from abroad. More than 3,000 are thought to have left to fight for extremist groups in Syria, Iraq and Libya over the past years.

(File photo: AFP/Getty)