TUNIS (REUTERS, AFP) - Gunmen wearing military uniforms stormed Tunisia's national museum on Wednesday, killing 17 foreign tourists and two Tunisians in one of the worst militant attacks in a country that had largely escaped the region's "Arab Spring" turmoil.

Five Japanese as well as visitors from Italy, Germany, Poland and Spain were among the dead in the noon assault on Bardo museum inside the heavily guarded parliament compound in central Tunis, Prime Minister Habib Essid said.

"They just started opening fire on the tourists as they were getting out of the buses ... I couldn't see anything except blood and the dead," the driver of a tourist coach told journalists at the scene.

Scores of visitors fled into the museum and the militants - who authorities did not immediately identify - took hostages inside, officials said.

Work was suspended at parliament during the attack.

Museum employee Dhouha Belhaj Alaya told AFP she heard "intense gunfire" around noon.

"My co-workers were screaming 'Run! Run! Shots are being fired!'" she said. "We escaped out the back door with co-workers and some tourists."

Security forces entered around two hours later, killed two militants and freed the captives, a government spokesman said.

A police officer died in the operation.

PM Essid said authorities were hunting for possible accomplices.

"There is a possibility, but it is not certain, that (the two gunmen) could have been helped," Essid said.

"We are currently conducting extensive search operations to identify the two or three terrorists who possibly participated in the operation."

Interior ministry spokesman Mohamed Ali Aroui told AFP that about 100 tourists had been inside the museum when the attack occurred.

At least four French citizens were among the wounded, a diplomatic source said.

Italy's foreign ministry said at least two of its citizens had been wounded and about 100 were taken to safety by police during the attack.

A cruise ship carrying more than 3,100 passengers, the Costa Fascinosa, was docked in Tunis at the time, and some of those aboard had gone ashore planning to visit the museum, the cruise line said.

A statement did not specify if any passengers were inside the museum at the time of the attack. But it said the ship's departure was likely to be delayed and that a support team was headed from Genoa to work with passengers and local authorities.

The attack on such a high-profile target is a blow for the small North African country that relies heavily on European tourism and has mostly avoided major militant violence since its 2011 uprising to oust autocrat Zine El-Abidine Ben Ali.

Several Islamist militant groups have emerged in Tunisia since the uprising, and authorities estimate about 3,000 Tunisians have also joined fighters in Iraq and Syria - raising fears they could return and mount attacks at home.

"All Tunisians should be united after this attack which was aimed at destroying the Tunisian economy," Prime Minister Essid declared in a national address.

The local stock exchange dropped nearly 2.5 per cent and two German tour operators said they were cancelling trips from Tunisia's beach resorts to Tunis for a few days.

Accor, Europe's largest hotel group, said it had tightened security at its two hotels in Tunisia.

US Secretary of State John Kerry said Washington condemned the attack and continued "to support the Tunisian government's efforts to advance a secure, prosperous, and democratic Tunisia."

Television footage showed dozens of people, including elderly foreigners and one man carrying a child, running for shelter in the museum compound, covered by security forces aiming rifles into the air.

State television said 17 tourists were killed.

Among the dead were three Italians, two Colombians and two Spaniards, their country's governments said.

The museum is known for its collection of ancient Tunisian artefacts and mosaics and other treasures from classical Rome and Greece.

There were no immediate reports that the attackers had copied Islamic State militants in Iraq by targeting exhibits seen by hardliners as idolatrous.

The museum's white-walled halls set in the parliament compound are one of the most popular tourist attractions in the Tunisian capital.

Work was suspended at parliament during the attack. Islamist lawmaker Monia Brahim told AFP gunfire from the initial assault prompted committees to suspend their meetings as lawmakers were ordered to assemble in the main chamber.

"There was enormous panic," another lawmaker, Sayida Ounissi, wrote on Twitter, saying the attack took place during hearings on Tunisia's anti-terrorism law.

Shocked but defiant, hundreds of Tunisians later gathered in the streets of downtown Tunis waving the country's red and white crescent flag, and chanting against terrorism.

"I pass this message to Tunisians, that democracy will win and it will survive," President Beji Caid Essebsi said in a television statement.

"We will find more ways and equipment for the army to wipe out these barbarous groups for good."

A MODEL OF COMPROMISE

Tunisia's uprising inspired "Arab Spring" revolts in neighbouring Libya and in Egypt, Syria and Yemen. But its adoption of a new constitution and staging of largely peaceful elections had won widespread praise and stood in stark contrast to the chaos that has plagued those countries.

After a crisis between secular leaders and the Islamist party which won the country's first election, Tunisia has emerged as a model of compromise politics and transition to democracy for the region.

But security forces have clashed with some Islamist militants, including Ansar al-Sharia which is listed as a terrorist group by Washington, mostly in remote areas near the border with Algeria.

Affiliates of Islamic State militants fighting in Iraq and Syria have also been gaining ground in North Africa, especially in the chaotic environment of Tunisia's neighbour Libya, where two rival governments are battling for control.

A senior Tunisian militant was killed while fighting for Islamic State in the Libyan city of Sirte over the past week. Security sources said he had been operating training camps and logistics.

The country is also fighting against the radicalisation of Muslim youth. Authorities say as many as 3,000 Tunisians have gone to Iraq, Syria and neighbouring Libya to fight in militant ranks, including with the Islamic State group.

Some 500 militants are believed to have since returned home.

Wednesday's assault was the worst attack involving foreigners in Tunisia since an Al-Qaeda suicide bombing on a synagogue killed 21 people on the tourist island of Djerba in 2002.

A militant blew himself up at the Tunisian beach resort of Sousse in late 2013 but no one else was killed or wounded.

Essebsi said the "top priority" for the government, which took office last month after Tunisia's first free elections, is "providing security and the battle against terrorism."

Tunisia kicked off the Arab Spring with its overthrow of Ben Ali and has taken pride in forming a stable and democratic government.

It is hoping to rebuild its once-burgeoning tourism industry, which is struggling to recover from the effects of the 2011 revolution.

Tourist arrivals dropped by 3 per cent last year.

Mohzen Marzouk, a presidential adviser, said Wednesday's attack "targeted our economy".

"But we cannot let this blow affect us. And I'm sure the world will keep its confidence in us," he said.