Tunisian security forces killed seven "terrorists" overnight near Ben Guerdane after a deadly jihadist attack on the town near the border with Libya, the authorities said on Wednesday.

The interior ministry said late Tuesday that five "terrorists" had been "eliminated" in the area, then on Wednesday said two more suspected jihadists had been killed.

Four Kalashnikov assault rifles were recovered, the interior and defence ministries said in a joint statement.

Tunisian media reports late Tuesday said security forces had surrounded a house where suspected jihadists were holed up in the Benniri area.

Benniri is a few kilometres (miles) south of Ben Guerdane which is still under curfew after Monday's dawn attack in which 36 assailants, 12 members of the security forces and seven civilians were killed.

The latest deaths take to 43 the number of suspected jihadists killed since the attack.

Schools nationwide observed a minute's silence early Wednesday ahead of funerals for some of the victims.

"It is vital to show students the importance of defending the nation, that the blood of martyrs did not flow for nothing," teacher Sonia El Kefi told AFP at a school in central Tunis.

"We will not allow terrorists to influence the minds of children."

The authorities said Monday's attack was an unprecedented assault by the Islamic State group aimed at setting up a new stronghold in the country across the border from Libya, where IS already has a presence.

Witnesses reported a massive security presence on Wednesday in Ben Guerdane, a town of 60,000 people.

The authorities have warned that mopping up operations after Monday's attack would continue.

Prime Minister Habib Essid said on Tuesday that about 50 extremists were believed to have taken part in the assaults on an army barracks and police and National Guard posts.

Defence ministry spokesman Belhassen Oueslati said 17 suspects were arrested on Tuesday near a military barracks and handed over to the National Guard for questioning.