I’d be shocked if ISIS wasn’t behind this, there are a huge number of Tunisians fighting for them in Syria and Iraq.

UPDATE: ISIS spokesman on why museum was attacked.

Update to this story:

Tunisian security forces arrested nine people linked to the deadly attack on the National Bardo Museum that left 23 dead, scores wounded and threatened the country’s fledgling democracy and struggling tourism industry, the president’s office said Thursday.

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

No one has claimed responsibility for the attack. Tunisia has faced scattered extremist violence, and a disproportionately large number of Tunisians have joined the Islamic State of Syria and Iraq (ISIS) to fight in those two countries. […]

Health Minister Said Aidi said the death toll rose Thursday to 23 people, including 18 foreign tourists, with almost 50 people wounded. Five Tunisians were killed, including two attackers. Aidi said all the injuries came from bullet wounds, and that several victims were brought in without identity documents.