AKIPRESS.COM - "Islamic State" (IS) posted an audio message online on Thursday, claiming responsibility for the attack on Tunisia's National Bardo Museum, AFP reports.

"Two knights from the Islamic State... heavily armed with automatic weapons and grenades, targeted the Bardo Museum," the message said. The group threatened more attacks, saying: "What you have seen is the first drop of the rain."

The statement said the two attackers were shot dead by security forces only because they had run out of ammunition, AP reports.

IS, based in Syria and Iraq, has affiliates in neighboring Libya, where many Tunisians have joined extremist groups. A prominent Tunisian field commander fighting with IS was kiilled in Syria earlier this week.

On Thursday, Tunisia's government announced that police had made the first arrests after the attack, which killed at least 20 people.

News agencies have given conflicting figures on the number of dead, which ranges between 20 and 25, DW reports.

Most of those killed appeared to have been European tourists, with an official at the hospital where many victims were taken saying they had confirmed the identities of Spanish, British, Belgian and French nationals. Also among those identified were victims from Japan, Australia and Colombia.

There was some good news, with the discovery in the morning of two Spanish tourists who survived the attack after hiding from the gunmen and spending the entire night in the museum.