From BBC:

The attack on the famous Bardo museum in the capital, Tunis, was the deadliest since the revolution, with at least 19 people – mostly European tourists – killed. No group has said it carried out the attack, but Tunisian officials have pointed at fighters linked to the Islamic State (IS), which is fighting in Iraq and Syria and has a foothold in neighbouring Libya. Tunisian authorities say up to 3,000 of its citizens have gone abroad to wage jihad – including to Syria and Iraq – making them the largest number of foreign fighters to join IS’s ranks, according to some researchers.