Tunisia's president has urged his country to stand united in the face of armed groups who intend on attacking the country, after an attack on the national museum killed 21 people.

Speaking in the city of Carthage on Friday, at a ceremony marking the country's 59th anniversary of independence from France, President Beji Caid Essebsi laid out  some of the country's challenges, starting with state security.

"The first challenge is the security challenge and the challenge of winning the war against terrorism," said Essebsi.

"Tunisia is today in a war against terrorism. We won't win if we don't stand together. The conditions of the national unity are provided today." 

The two gunmen who stormed the National Bardo Museum killing 21 people on Wednesday were named by authorities as Yassine Abidi and Hatem Khachnaoui and were killed in a security operation that followed the assault on the museum.

Rafik Chelly, the country's secretary of state for security said on Friday that the two gunmen trained at a camp for fighters in Libya.

The gunmen opened fire on the tourists - including visitors from Japan, Italy, France, Australia, Colombia, Poland and Spain - as they got off a bus then chased them inside the museum. 

It sparked outrage, with hundreds of people gathering later in a major thoroughfare of the capital, singing the national anthem and shouting slogans against the attackers, labelling them "terrorists".

'Sleeper cells'

Officials said no formal links to a particular armed group had been established, although the Islamic State of Iraq and the Levant (ISIL) group reportedly released audio recordings claiming responsibility for the attack on the National Bardo Museum in the capital city of Tunis.

Chelly said the two gunmen had been "from sleeper cells" present in several areas. He also named locations of several suspected training camps for Tunisians in Libya, including the second city Benghazi and the coastal town of Derna, which has become a stronghold for armed groups. 

France stepped up to offer Tunisia material and intelligence help in fighting off such armed groups and strengthening its border security.

"The state has been considerably weakened by its porous borders between Libya and Tunisia," he told reporters. "The control of borders is important and we can work on it by mobilising our skills and means," said French Interior Minister Bernard Cazeneuve speaking at the independence day ceremony on Friday.

The attack appeared to be the worst on foreigners in Tunisia since an al-Qaeda suicide bombing of a synagogue killed 14 Germans, two French and five Tunisians on the island of Djerba in 2002. 

Authorities say as many as 3,000 Tunisians have gone to Iraq, Syria and Libya to join ISIL, raising fears of battle-hardened fighters returning home to plot attacks.

Source: Al Jazeera and agencies