TUNIS - The Islamic State jihadist group Monday claimed responsibility for a knife attack in Tunisia the previous day which killed one National Guard officer and badly wounded another.

Three assailants were shot dead in an ensuing firefight Sunday in the same tourist district of the coastal city of Sousse, the National Guard said, labeling the attack a "terrorist" act.

The IS said Monday its "fighters" had carried out the attack, in a brief statement by its propaganda arm Amaq on the Telegram messenger service.

Tunisian authorities said Monday they had arrested seven people over the attack in which the assailants had rammed the officers with a vehicle and then stabbed them.

The wounded officer was "in a stable condition" on Monday, interior ministry spokesman Khaled Hayouni told AFP.

Since Sunday, "43 people have been questioned and seven of them arrested," Guard spokesman Houcem Eddine Jebabli told private station Radio Shems.

They included "the wife of one of the assailants, who described her husband as a 'martyr' during the interrogation," he said.

Two brothers of one of the attackers and a person suspected of recruiting them were also arrested, he added.

He said the attackers were a pair of twins and a third man from the marginalized northwestern region of Siliana, he said, without confirming or denying reports of a fourth attacker.

Jebabli said the twins had visited Facebook pages dealing with "explosive and armed attacks" but had stayed under the radar of the authorities.

Tunisia, since its 2011 revolution, has been hit by a string of jihadist attacks that have killed dozens of security personnel, civilians and foreign tourists.

Sunday's incident took place close to the site of the deadliest attack, when 38 people, most of them Britons, were killed in a 2015 beachside shooting rampage.