THE Islamic State group yesterday claimed responsibility for the deadly attack on Tunisia’s national museum that killed 23 people, most of them tourists.

The statement described Wednesday’s attack as a “blessed invasion of one of the dens of infidels and vice in Muslim Tunisia” and appeared on a forum that carries messages from the group.

The statement said there were two attackers and they weren’t killed until they ran out of ammunition. It promised further attacks.

“Wait for the glad tidings of what will harm you, impure ones, for what you have seen today is the first drop of the rain,” the statement.

IS, which is based in Syria and Iraq, has affiliates in neighboring Libya, where many Tunisians have gone to fight and train with extremist groups.

Earlier this week, a prominent Tunisian field commander for IS was killed in fighting inside Libya.

Tunisian Security forces have arrested nine people linked to the museum attack that left scores wounded and threatened Tunisia’s fledgling democracy and struggling tourism industry, the president’s office said yesterday.

The statement said five of those arrested were directly connected to the attack by two gunmen while the other four were arrested in the center of the country and part of a cell supporting those involved.

One of the gunmen was known to intelligence services, but no formal links to a particular extremist group have been established, Prime Minister Habib Essid said.

The attack was the worst at a tourist site in Tunisia in years, and a leading cruise line said it was canceling its Tunisian stops.

Razor wire ringed the museum yesterday and security forces guarded major thoroughfares in the capital as authorities hunted for two or three more people believed to have been involved in the attack.

Wednesday’s two attackers burst from a vehicle wielding assault rifles and began gunning down tourists climbing out of buses. The attackers then charged inside to take hostages before being killed in a firefight with security forces.

A Spanish man and a pregnant Spanish woman who survived hid in the museum all night in fear and were retrieved safely yesterday morning by security forces.

Essid, in an interview with France’s RTL radio, said Tunisia was working with other countries to learn more about the attackers, identified as Yassine Laabidi and Hatem Khachnaoui.

He said Laabidi had been flagged to intelligence, although not for “anything special.”

The attack spells oceans of trouble for the tourism industry, which brings throngs of foreigners every year to Tunisia’s Mediterranean beaches, desert oases and ancient Roman ruins — and which had just started to recover after years of slump.

Health Minister Said Aidi said 18 foreign tourists were among the dead, with almost 50 people wounded. Five Tunisians, including the two attackers, were killed. Aidi said all the injuries came from bullet wounds.

Moncef Hamdoun, an official with the Charles Nicolle hospital where many victims were taken, said seven of the dead remain unidentified. He listed the dead as three Japanese women, a Spanish man and a Spanish woman, a Colombian woman, an Australian man, a British woman, a Belgian woman, a Frenchman and a Polish man.

One victim, identified in Japanese media as 66-year-old Machiyo Narusawa, was among a group of 70 Japanese tourists who traveled from Tokyo.

Travel agency Cruise Planet said many on the tour were retired couples.

Announcing the news that a British tourist was among the dead, Prime Minister David Cameron vowed to fight against extremists “with everything we have.”

“We will not let terrorists undermine democracy,” he said in a tweet.

The tourist, named as Sally Adey, was on an excursion to the museum with her husband. He survived the attack, officials said.

“These terrorist attacks yesterday in Tunisia were an appalling and brutal outrage,” Cameron said.

“This is the latest example of extremist terror and we have to fight it with everything we have,” he said.

“We mustn’t let democracy, freedom, the rule of the law, the things we hold dear, and people in Tunisia hold dear, we must not let them be defeated or undermined by these extremists and terrorists.

“That is the battle we are engaged in but I’m confident if we stick to our values we will win through.”

In a separate statement, UK Foreign Minister Philip Hammond condemned a “despicable act” and said: “The Tunisian people are rightly proud of their democratic transition.

“Cowardly attacks, such as the one we saw yesterday, must not be allowed to undermine what they have achieved,” he said.

A woman from Belgium was among those killed in the attack, a Belgian foreign ministry official said, hours after she had been reported as missing.

“Embassy staff were able to check the list of those killed in the attacks and one of the victims is Belgian,” said spokesman Joren Vandeweyer.

Foreign Minister Didier Reynders told Belga news agency that the woman’s husband, who was injured in the attack, identified his wife among the victims after undergoing a knee operation.

According to broadcaster RTL, the 61-year-old was from Antwerp and the mother of two daughters.

The couple had been unaccounted for on the Costa Fascinosa cruise ship, which had dropped anchor in Tunis with more than 3,100 passengers on board.

A Tunisian translator for Polish tourists, Abdelwaheb Khedimi, told TVN24 that he was standing across the street from the museum gate when he saw two men run through the gate, produce automatic weapons and start firing in the direction of some 10 tour buses in the museum’s parking lot.

A Polish military plane arrived in Tunis yesterday morning to bring back Polish tourists who want to return home. Polish President Bronislaw Komorowski said some people from Poland are still missing, and Polish prosecutors say they will open their own investigation into the attack

Meanwhile, Ifriqiyah Media, which has aired claims from Tunisian extremists in the past, posted what it said were details about the attack, according to the SITE Intelligence Group, which monitors extremist activity online.

Tunisian legislator Bochra Belhaj Hmida, of the secular majority party Nida Tunis, told AP that about 2,000 suspected terrorists are believed to be in Tunisia, many of whom joined extremists in Iraq or Syria then returned home.

“They are in a situation of being lone wolves, where each of them is free to do the actions they want,” she said.

“These are people who are let loose with weapons and wherever they can strike, they will not forgo the opportunity.”