One of the deadliest clashes seen so far between Tunisian forces and extremist attackers left at least 53 people -- including 35 terrorists -- dead Monday near Tunisia's border with Libya, the government said.

The fighting in the border town of Ben Guerdane in eastern Tunisia comes amid increasing concern that violent extremism in Libya could destabilize the region.

"This is an unprecedented attack, planned and organized, and whose goal was probably to take control of this area and to announce a new emirate," said Tunisian president Beji Caid Essebsi.

The government closed its two border crossings with Libya following the attack that left 35 terrorists, seven civilians and 11 members of Tunisia's security forces dead, the Tunisian interior and defense ministries said in a statement.

A 12-year-old girl was among those who were killed.

Libya's chaos, five years after the uprising that led to the ouster and killing of longtime autocrat Moammar Gadhafi in 2011, has allowed the Islamic State group to take control of several cities. The divided country is ruled by two parliaments: an internationally recognized body based in the eastern city of Tobruk and a rival government, backed by Islamist-allied militias, that controls the capital, Tripoli.

Tunisia's fledgling democratic government is especially worried about the presence of ISIS in Libya after dozens of tourists were killed in extremist attacks in Tunisia last year.

At dawn Monday, gunmen targeted a police station and military facilities in Ben Guerdane, Interior Ministry spokesman Yasser Mosbah told The Associated Press. A night curfew has been ordered in Ben Guerdane until further notice.

No group has yet stepped forward to claim responsibility for the attacks but members of the Jihadist forum community commenting on two ISIS-affiliated websites said ISIS militants were engaged in the fighting.

France's foreign ministry condemned the attacks and identified the gunmen as "terrorists coming from Libyan territory."

"This attack is just reinforcing the urgent need for a political solution in Libya," the ministry said in a statement, adding that Tunisia was targeted because of its "exemplary democratic transition."

The Tunisian military sent reinforcements and helicopters to the area around Ben Guerdane and authorities were hunting several attackers still at large. Officials urged residents to stay indoors.

Last week, Tunisian security forces killed five heavily armed men in an hours-long firefight after they crossed into the country from Libya with a larger group. Tunisian security forces had been placed on alert based on "precise information" of possible border infiltrations following a Feb. 19 U.S. raid on an IS camp near the Libyan town of Sabratha, not far from the Tunisian border, the statement said.

Defense Minister Farhat Horchani said last week that German and American security experts were expected in Tunis on Monday to help Tunisia devise a new electronic video-surveillance system of its border with Libya.

Tunisia was targeted last year by three attacks that left 70 people dead and were claimed by ISIS. According to Tunisian authorities, the attackers had been trained in Libya.