The gunman behind an attack on a Tunisian hotel near Sousse Friday that left at least 27 people dead was a Tunisian student previously unknown to police, a top official said.

"He is Tunisian, originally from the Kairouan region (in central Tunisia). He is a student," Secretary of State for Security Rafik Chelly told Mosaique FM radio.

"This person was not known (to us)," he added.