Tunisia's Interior Ministry says security forces leading a counter-terrorism sweep have killed five suspected extremists in central Tunisia.

The operation by the national guard and the army near the town of El Ktar in the Gafsa region comes less than a week after Tunisia's government declared a state of emergency following a gunman's attack in the beach resort of Sousse that left 38 tourists dead - mostly Britons.

Ministry spokesman Walid Louguini said a gunfight erupted as a special national guard unit tracked and chased eight suspected extremists in the mountainous Ouled Bouomrane area, near Gafsa's mining zone.

He said the operation was continuing.

The UK yesterday urged all British tourists to leave Tunisia, saying an extremist attack was "highly likely" despite enhanced security measures.