At least six people were wounded on Friday when a bomb went off along railway tracks in southwestern Pakistan, halting train service in the region, security and railways officials said.

The train was travelling from Baluchistan's capital of Quetta to the eastern metropolis of Lahore when a blast on the main railway track damaged one of its cars.

"One train bogie was damaged in the blast and a portion of the tracks blown up," said railways official Aammir Baloch, adding that Quetta's train services had been suspended.

Security officials said six passengers were injured in the blast.

The Taliban, Sunni Islam militants and sectarian groups linked to al Qaeda and the Islamic State group also operate in the strategically important region, which borders Iran and Afghanistan.

Baluchistan is at the centre of infrastructure projects that form part of China's 'Belt and Road' initiative, which has brought $57 billion of investment to Pakistan.

Violence in the southwestern region has fuelled concern about security for a transport and energy link planned to run from western China to Pakistan's southern deepwater port of Gwadar.

Separatists in Baluchistan, who have long battled the state for a greater share of the resources of the gas- and mineral-rich region, also accuse the central government of discrimination.

Separately, two workers of a prominent political party were killed on Friday in a landmine blast in the district of Harnai near Quetta as they travelled to a party meeting.

"The victims were brothers and belonged to the Awami National Party," regional official Abdul Salam Achakzai told Reuters.

"The explosive device was planted by the road," he added.