At least nine suspects have been arrested in Tunisia, as the country heightens security measures following the terror attack which killed 20 foreign tourists.

Shortly after the Islamic State (Isis) claimed responsibility for the attack on the National Bardo Museum in Tunis, security agencies detained the suspects who are thought to be directly involved.

A statement from the presidential office said: "Security forces were able to arrest four people directly linked to the [terror] operation and five suspected of having ties to the cell."

Fearing a quick blow to the country's tourism-driven revenue, the government beefed up security measures across Tunisia, rolling out soldiers on the streets of various cities. "The president has decided large cities will be secured by the army," the presidential statement added.

Twenty of the 23 people killed in the attack were foreign tourists from countries including Britain, Japan, Spain and Italy.

Tunisia's Interior ministry official Rafik Chelli, cited by Reuters, said the two assailants who were killed in the attack were trained in jihadist camps in Libya. The two gunmen were identified as Yassine Laabidi and Hatem Khachnaoui

Alongside the arrests, Prime Minister Habib Essid said: "The operation is underway, we have good leads. Honestly speaking, there have been arrests. But we hope that when the operation is completed, we will have final results and we will be ready to give you all the details."

Authorities in the north African country are also thought to be working with investigators from other foreign agencies to deal with the situation.

US officials have said the Tunisia attack is consistent with other operations carried out by the IS-backed militants, suggesting a heightened security threat in the region as the Iraq-based extremist group is quickly spreading its tentacles in the volatile conflict zones.

"The tactics we saw used at the Bardo Museum would be entirely consistent with tactics that ISIL [another acronym of IS] has previously used that show a blatant disregard and even a brutality for innocent civilians," said White House press secretary Josh Earnest.