Three Chinese nationals and two Mauritanians were kidnapped in southwest Mali on Saturday, the country's armed forces said, in the latest attack in the war-torn Sahel state.

Armed men attacked a construction site 55 kilometres (34 miles) from the town of Kwala, making off with five pick-up trucks and the hostages, Mali's army said on social media.

The assailants also destroyed equipment including a crane and dump trucks belonging to Chinese construction firm Covec, and Mauritanian road-building company ATTM, according to the army.

A Malian army official, who requested anonymity, said the kidnap victims were working on road construction in the region. "The release of all the hostages is our priority," he said.

Mauritania's Al-Akhbar news agency reported that gunmen arrived on motorbikes to attack the construction site, burning equipment as well as fuel tanks before withdrawing with captives.

AFP could not independently verify this account.

Mali has been struggling to contain an Islamist insurgency that first broke out in the north of the country in 2012 before spreading to the centre and neighbouring Burkina Faso and Niger.

Thousands of people have been killed and hundreds of thousands have fled their homes, while the economic impact on one of the world's poorest countries has been devastating.

Abductions have been frequent, both of Malians and of foreigners.

French journalist Olivier Dubois was abducted in northern Mali on April 8, for example. 

He said in a hostage video that the Group to Support Islam and Muslims (GSIM), the largest jihadist alliance in the Sahel, had kidnapped him.