TUNIS, Tunisia (AP) — Tunisian news reports say a national guard chief and three extremists have been killed in a clash near the Algerian border on the first day of Tunisia's presidential campaign.

Radio Mosaique reported that national guard officers opened fire Monday on an extremist group trying to cross the region of Kasserine from the Kef mountains.

Citing local sources, the report says the security operation is ongoing near the town of Hidra. Mosaique and daily Al-Chourouk reported that four people have been killed: a guard chief and three militants.

The clash came on the day Tunisia's presidential campaign is officially opening, after the country's first democratically elected president died in office in July.

Tunisian leaders have struggled to contain Islamic extremism in recent years, notably along its borders with Algeria and Libya.