A Tunisian policeman stands guard at Bourguiba Avenue in the capital of Tunis during a celebration to commemorate Tunisia’s National Independence Day March 20, 2015.

Tunisian authorities said Saturday there were developments in the investigation into the attack on the national museum claimed by the Islamic State of Iraq and Syria (ISIS) group that killed 20 foreign tourists.

“There are developments in the case, but to protect the secrecy of the investigation we prefer not to provide any details,” prosecution spokesman Sofiene Sliti told AFP.

However, Interior Minister Mohamed Ali Aroui said “more than 10 people have been arrested for direct or indirect involvement in the attack, among them people who provided logistical support”.

He declined to say whether they included nine people already reported arrested, including the father, sister and two brothers of one of the gunmen police killed in the attack, Jabeur Khachnaoui.

A police source and acquaintance of Khachnaoui said the gunman’s four relatives had now been freed, but Aroui would not confirm that report.

On Wednesday, the two gunmen targeted tourists visiting the National Bardo Museum, killing 21 people, including a policeman.

The dead tourists were four Italians, three Japanese, three French, two Spaniards, a Colombian, an Australian-Colombian, a British woman, a Belgian woman, three Poles and a Russian.

Dr Chadli Dziri, chief of surgery at the Charles Nicolle hospital in Tunis, said that of 43 people wounded there were still concerns about the prognosis for one, a Frenchwoman shot in the stomach and the leg.

Dziri said it was clear that many people had been shot as they tried to escape, because they had been hit in the back.

On Thursday, the ISIS group claimed it was behind the attack and threatened more.

Authorities said the gunmen had trained in neighboring Libya, where the ISIS is believed to have training camps.

Tunisia has seen an upsurge in Islamist extremism since the 2011 revolution that ousted dictator Zine El Abidine Ben Ali and sparked the Arab Spring.

Tunisia has taken pride in forming a democratic government and achieving stability since the Arab Spring — in marked contrast to countries such as Egypt and Libya.

But dozens of police and military personnel have been killed in attacks blamed on Islamist militants.

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