Tunisia's main secular party was in a confident mood Monday with vote counting underway following a general election seen as critical for democracy in the cradle of the Arab Spring.

US President Barack Obama hailed the North African country's first parliamentary election since its 2011 revolution as "an important milestone in Tunisia's historic political transition".

Tunisians voted Sunday in an election seen as pivotal to establishing democracy in the cradle of the Arab Spring uprisings, with security forces deploying heavily to avert extremist attacks.

When polls opened at 7:00 am (0600 GMT), dozens of voters were already queuing outside one polling station in Marseille Street in central Tunis, an AFP correspondent reported.

Tunisia's prime minister warned Saturday of possible jihadist attacks during a landmark election this weekend, as security was tightened for a vote he said offered hope to the entire region.

"We know that this will be a target (for jihadist groups) because it is unique in the region. It brings hope," Mehdi Jomaa told Agence France-Presse during an inspection of security forces ahead of Sunday's poll.

A raid by Tunisian security forces on an armed group near the capital Friday left six suspected militants dead, including five women, fanning tensions days ahead of a landmark election.

Tens of thousands of soldiers and police will be deployed for Sunday's parliamentary polls -- the first since an uprising three years ago that inspired the Arab Spring revolutions.

Tunisia, fearing possible terrorist attacks, will close its border with politically unstable Libya for three days to coincide with this weekend's parliamentary election, the government said Thursday.

The Ras Jedir and Dehiba border crossings would be closed from Friday through election day Sunday for people travelling from Libya, except for diplomatic missions and in "exceptional and urgent cases," a statement said.

A Tunisian policeman was killed in a firefight near the capital Thursday amid fears of jihadist violence in the run-up to the first parliamentary election since the country's 2011 revolution.

"Our agent died of a bullet wound in the eye sustained in clashes with a terrorist group," a police official told AFP at the scene.

Tunisia's transition to democracy serves as an example of how to defeat extremists such as the Islamic State jihadist group, the leader of the country's powerful Islamist movement said.

"The success of the Tunisian experience is in the international interest, especially in the fight against extremism and the fight against Islamic State and similar groups," Ennahda head Rached Ghannouchi said in an interview with AFP in the runup to the country's first parliamentary election on Sunday since its 2011 revolution.

Within hours of his arrest by police, Walid Denguir was dead -- just one of many alleged torture victims at the centre of a fight for justice in post-revolution Tunisia.

More than three years since a pro-democracy uprising toppled long-time strongman Zine El Abidine Ben Ali, rights groups say change has been slow to reach the country's justice system.

When Hisham Missaoui was seriously wounded tracking suspected al-Qaida-linked jihadists near Kasserine, his family blocked the road to the restive Tunisian city with burning tyres and rubble.

Mired in poverty, Kasserine lies at the foot of Mount Chaambi, where the army and police have since 2012 been hunting down jihadists blamed for deadly attacks on security forces.

Tunisians vote Sunday to elect their first parliament since the country's 2011 revolution, in a rare glimmer of hope for a region torn apart by post-Arab Spring violence and repression.

After three weeks of largely low-key campaigning, more than five million voters are to elect 217 deputies in a ballot pitting the Islamist Ennahda movement -- the country's largest party -- against a host of secular groups.