Attackers with knives killed a Tunisian National Guard officer and wounded another Sunday before three assailants were shot dead in a firefight, the security force said, labelling it a "terrorist" act.

The attack took place in the tourist district of the coastal city of Sousse, the site of the worst of several terrorist attacks in recent years, where 38 people, most of them Britons, were killed in a 2015 beachside shooting rampage.

"A patrol of two National Guard officers was attacked with a knife in the centre of Sousse," 140 kilometres south of the capital Tunis, said National Guard spokesman Houcem Eddine Jebabli.

"One died as a martyr and the other was wounded and is hospitalised," he said, adding that "this was a terrorist attack".

The attackers had first rammed the officers of the national gendarmerie with a vehicle, said the interior ministry in a statement.

After the knife attack, security forces pursued the assailants, who had taken the officers' guns and vehicle, through the Akouda district of the city's tourist area of El-Kantaoui, said Jebabli.

"In a firefight three terrorists were killed," he said, adding that security forces "managed to recover" the car and two pistols the assailants had stolen.

British ambassador to Tunisia Louise de Sousa tweeted she was "appalled to hear of the attack on a National Guard patrol in #Sousse this morning.

"My sincere condolences to the family of the murdered officer and I wish a swift recovery to the injured. #UKsupportTunisia"

Series of attacks 

Tunisia, since its 2011 popular revolution, has been hit by a string of terrorist attacks that have killed dozens of security personnel, civilians and foreign tourists.

A suicide attack against security forces protecting the US Embassy in Tunis killed a Tunisian police officer and left several others wounded in March.

2015 was a particularly bloody year, with three major deadly attacks claimed by the Daesh terror group.

An attack at the capital's Bardo museum in March killed 21 foreign tourists and a security guard.

Just three months later, the 38 tourists were killed in the shooting rampage at Sousse.

And that November, a bomb blast on a bus in central Tunis killed 12 presidential guards.

While the situation has significantly improved since then, Tunisia has maintained a state of emergency.

Assaults on security forces have persisted, mainly in remote areas along the border with Algeria.

Tunisia has been praised as a rare success story among the 2011 Arab Spring popular uprisings that swept the region and brought down many autocrats, among them Tunisia’s long-time president Zine El Abidine Ben Ali.

But the small Mediterranean country of about 11 million people is mired in an economic crisis, with the official unemployment rate at 18 per cent, and in need of new assistance from the International Monetary Fund.

Last week Tunisia’s parliament approved a new technocratic government led by Prime Minister Hichem Mechichi which faces the task of tackling deep social and economic woes in the North African country.

The 46-year-old premier pledged to revitalise the economy, including the crucial tourism sector, which had rebounded after the jihadist attacks but has been hit hard this year by the coronavirus pandemic.