Islamist fighters attacked army and police posts in the Tunisian town of Ben Guerdane near the border with Libya early on Monday in clashes that killed at least 45 people, including 28 militants, the government said.

The militants, six members of the National Guard, two policemen, a customs official and a soldier died after the militants attacked security posts in the border town of Ben Guerdane at dawn, the interior and defence ministries said in a joint statement.

Seven civilians were also killed in the clashes, the statement said, adding that the death toll was preliminary.

Tunisian radio station Mosaique FM said the clashes began at 4.30am (3.30am GMT) and residents told AFP that it was still raging after daybreak. Authorities warned people to stay in their homes as gunfire erupted in the town centre.

Bodies of dead militants lay in the street near the army barracks, witnesses said.

"I saw a lot of militants at dawn. They were running with their Kalashnikovs," Hussein, a local resident, told Reuters by telephone. "They said they were [the Islamic State group] and they came to target the army and the police."

Authorities sealed off the nearby beach resort town of Djerba, a popular destination for foreign and local tourists, according to the TAP state news agency.

Tunisian troops have been on alert in the border area following reports that militants had been slipping across since a US air strike on an Islamic State (IS) group training camp in Libya on February 18 killed dozens of Tunisian militants.

At least four of the five militants killed in the hour-long firefight near Ben Guerdane last Wednesday were Tunisians who had entered from Libya in a bid to carry out attacks in their homeland, the interior ministry said.

Border strife

Deadly attacks by the IS group on foreign holidaymakers last year, which dealt a devastating blow to Tunisia's tourism industry, are believed to have been planned from Libya.

Tunisia has built a 200km barrier that stretches about half the length of its border with Libya in an attempt to stop militants infiltrating.

Last month's US strike on the IS group training camp outside the Libyan city of Sabratha targeted Noureddine Chouchane, the suspected mastermind of two of last year's attacks.

Washington has said Chouchane was likely among the dozens of militants killed, and that the strike probably averted a mass shooting or similar attack in Tunisia.

Britain announced last week that it was sending a team of around 20 soldiers to Tunisia to train troops patrolling the border with Libya.

Thirty Britons were among 38 foreign holidaymakers killed in a gun and grenade attack on a beach resort near the Tunisian city of Sousse last June.

And last March, jihadist gunmen killed 21 tourists and a policeman at the Bardo Museum in Tunis.

According to a UN working group on the use of mercenaries, more than 5,000 Tunisians, mostly aged 18 to 35, have travelled abroad to join jihadist groups.

(FRANCE 24 with AFP and REUTERS)