Nine people suspected of links with the gunmen who attacked a Tunis museum leaving 21 dead have been arrested, the presidency announced Thursday.
"Security forces were able to arrest four people directly linked to the (terrorist) operation and five suspected of having ties to the cell," it said in a statement, without giving details.
Twenty foreign tourists were among those killed in Wednesday's attack on the national museum. There has been no claim of responsibility.
The presidency did not identify the suspects or say what role they played in the deadly attack.
But it stressed Tunisia was facing "exceptional circumstances" and that "terrorist operations have now moved from the mountains to the cities."
And it announced measures to bolster the armed forces and police and to reinforce security along porous borders with conflict-hit Libya and Algeria.
Tunisia has seen an upsurge in Islamist extremism since the 2011 revolution that ousted longtime strongman Zine El Abidine Ben Ali, sparking Arab Spring uprisings.
An army offensive against the jihadists, who are linked to Al-Qaeda in the Islamic Maghreb, has been under way since 2012 in the Mount Chaambi region near the Algerian border.
Dozens of police and military personnel have been killed since the offensive was launched.