TOKYO (AFP) - Japanese Prime Minister Shinzo Abe said on Thursday at least three nationals were killed when gunmen stormed Tunisia's national museum, in what his government condemned as a "despicable act of terrorism".

Tunisian Prime Minister Habib Essid had earlier said five Japanese were among the 17 foreign tourists killed in the attack.

"At the moment, we know three Japanese nationals are dead and three injured," Mr Abe told reporters.

"No matter what the reasons were, terrorism can never be forgiven. We strongly condemn this," he said, adding that Tokyo was still working to collect information. "We will exert the utmost effort in our fight against terrorism by deepening cooperation with the international community."

Speaking to reporters earlier in the day, Foreign Minister Fumio Kishida labelled the attack a "despicable act of terrorism."

Among the injured Japanese was Ms Noriko Yuki, 35, who was visiting the museum with her mother.

"I was crouching down with my arms over my head, but I was shot in the ear, hand and neck," she said from her hospital bed, in footage broadcast by NHK.

"My mother beside me was shot in the neck. Mother couldn't move by herself when the police came over."

In the footage, Ms Yuki did not say exactly what had happened to her 68-year-old mother, only that she was rushed to a separate hospital for surgery.

The assault on Wednesday raised fears for the birthplace of the Arab Spring.

The brazen daylight raid sparked panic at the nearby Parliament and the National Bardo Museum itself, a magnet for the tourists who contribute so much to the economy.

Among the dead were five Japanese, four Italians, two Colombians and one each from Australia, France, Poland and Spain, the Tunisian prime minister said.

It was the second time Japan has become embroiled in Middle East violence this year after the execution-style murders of a journalist and his friend by Islamist extremists in January.