Tunisian security forces have fought a gun battle with armed men in pick-up trucks near the Libyan border, officials say.
The gunmen were reportedly driving vehicles with Libyan licence plates.
The violence broke out late on Friday and lasted into early Saturday, with Tunisian officials saying some of the attackers had been injured.
Thousands of Libyans have streamed into Tunisia to escape fighting between rebels and Muammar Gaddafi's forces.
A Tunisian official told the AFP news agency that a patrol was sent out on Friday evening after a local resident reported suspicious vehicles near the border.
Between five and eight Libyan vehicles were involved in the skirmish, which lasted several hours, according to the official.
Military sources said no Tunisian personnel were hurt, but the attackers, who were still being hunted, had suffered casualties.
Some reports claimed the attackers were Libyan, but there was no indication whether they were aligned with any of the sides in the country's civil conflict.