Four people have been arrested by Tunisian forces in connection with the terror attack at the Bardo museum in the capital which killed 21 people, according to the President's office.
Tunisia's army is also being deployed to major cities to "increase security".
"After a meeting with the armed forces, the president has decided large cities will be secured by the army," the Presidency said in a statement.
A cruise ship passenger on a stopover in Tunisia has told ITV News how his wife was shot dead at his side in the country's museum attack.
A woman who was shot by terrorists in Tunisia's museum attack says she smeared herself with victims' blood and played dead to survive.
Tunisia was an obvious target for Islamic militants but today's attack on the place where the Arab Spring began is particularly depressing.