TUNIS, Tunisia (AP) — Tunisian security forces killed five heavily armed men in an hours-long firefight Wednesday after they crossed into the country from Libya with a larger group.

An Interior Ministry statement said that a civilian was also killed by a stray bullet and a Tunisian army officer was wounded in the exchanges of fire. It said the five were killed after taking refuge in a home while an unspecified number of others fled.

The group entered Tunisia at the Ben Guerdane border post, and the area was quickly surrounded, the ministry said.

Tunisian security forces had been placed on alert based on "precise information" of possible border infiltrations following the Feb. 19 U.S. raid on an Islamic State group camp near the Libyan town of Sabratha, not far from the Tunisian border, the statement said. Six Kalashnikov rifles, a large quantity of ammunition and two pick-up trucks were seized, it added.

Also Wednesday, a Tunisian court convicted 75 people on terror-related charges — 37 of them in absentia. All but three of the sentences were ranging from one to 21 years.

Three men, two of them extremist leaders, were sentenced to death — all in absentia. Among them was Algerian Khaled Chaied, considered the head of the Oqba Ibn Nafaa brigade, believed to be linked to al-Qaida's North African arm, and two Tunisians, including Mourad Gharsalli, another Oaba Ibn Nafaa leader accused of links to prominent warlords in Algeria and Mali.

Tunisia, a fledgling democracy, is deeply engaged in fighting Islamist extremists after two attacks last year that killed 60 people, mostly tourists, on a beach resort and at a major museum outside Tunis, the capital.