LIBYA (REUTERS) - At least 45 people, including civilians and a customs agent, were killed in clashes not far from a beach resort town near the Libya-Tunisia border.

The fighting began with an attack by Islamist militants on a police barracks in the Tunisian town of Ben Guerdan.

Residents say the assault was carried out by ISIS, raising concerns about a potential spillover of fighting from Libya, where the group is ramping up its presence.

Tunisia has been targeted by the militants several times over the past year, with high profile attacks on sites popular with tourists.

With Western help, the government says its security forces will continue to fortify the border to try to keep ISIS out and prevent further attacks.