TUNIS - Suspected Islamist militants captured and killed a Tunisian police officer, stabbing him and slashing his throat as he travelled home off-duty south of the capital, the government said on Sunday.

Nine suspected militants were arrested after the officer was killed on Saturday night near El Fahes in the Zaghouan region, around 60 km (37 miles) southwest of Tunis, the interior ministry said.

Tunisia has been praised for its young democracy after its 2011 uprising toppled autocrat Zine El-Abidine Ben Ali and allowed free elections and a new constitution.

But Islamist militants are waging a campaign against security forces, who are trying to flush them out from the Chaambi mountains bordering Algeria.

Authorities are also worried about Islamist extremists using remote, desert areas of neighbouring Libya as a base.

Tunisia is one of the Arab world's most secular countries, but the North African state is also a key source of foreign jihadist fighters travelling to Syria and Iraq to join Islamic State militants and other extremist groups there.