Gunmen killed six labourers in an overnight raid in Pakistan's southwestern Balochistan province, officials said Saturday, in the region's latest bout of violence.

Balochistan has been plagued for decades by a separatist insurgency as well as sectarian killings, and attackers have a history of targeting workers seen as outsiders in the region.

Two local officials said the attack took place in Turbat city -- 120 kilometres (75 miles) east of the border with Iran -- where ethnic Punjabi labourers were constructing a private residence.

"Gunmen entered an under-construction house and attacked eight sleeping labourers," Saeed Ahmed Umrani, a senior local administration official, told AFP.

"Six were killed on the spot while the remaining two are critically injured," he added.

Hussain Jan, another local official, confirmed the casualties and said "raids were conducted in the area to trace the assailants".

Ethnic Baloch militants have been fighting for more control over Balochistan, the largest but poorest of Pakistan's provinces despite its abundant natural resources.

They have in the past targeted ethnic Punjabis and Sindhis from elsewhere in Pakistan, as well as foreigners working for energy firms they believe are exploiting the region without sharing its riches.