Unidentified gunmen lined up miners at a small private coal mine in southwestern Pakistan and shot them on Friday, police and media said, killing at least 20 and wounding seven in rising violence in the restive region.

The attack early in the morning in the mineral-rich province of Balochistan that borders Afghanistan and Iran, is the worst in weeks and comes days ahead of the country hosting a summit of the Eurasian group Shanghai Cooperation Organization.

It also comes as Islamabad hosts a delegation from Saudi Arabia that is exploring mining deals in the South Asian country trying to recover from an economic crisis.

No group claimed responsibility for Friday's attack, in which the dead included four Afghan nationals while four others from the country were injured.

"A group of armed men attacked the Junaid Coal company mines in the Duki area in the wee hours using heavy weapons," said Humayun Khan, the police station house officer for the town, located east of the city of Quetta.

They fired rockets and grenades at the mines as well, he added.

The attackers gathered the miners at one place and opened fire on them, local media reported, and officials said that they also destroyed equipment and set mining machinery on fire.

Balochistan has been troubled for decades as Baloch insurgent groups fight against the state, saying it denies them their share of regional resources.

Several of the attacks have targeted migrant workers, many of who - including from Afghanistan - are employed by smaller, privately operated mines.

There are ten coal mines located in the area, a company official told local media.

"We have received 20 bodies and six injured so far at the district hospital," said Johar Khan Shadizai, a doctor in Duki.

Prime Minister Shehbaz Sharif called for a report on the incident, and stated that the government was "determined to root out all forms of terrorism".

"The provincial government has ordered an investigation and the case has been registered against unknown assailants under terrorism law," an official said.

Pakistan has seen a resurgence of Islamist militancy since 2022 when a ceasefire between the Pakistani Taliban and the government broke down.

Two Chinese nationals working for a power plant were killed in an explosion near the international airport in Karachi city earlier this week.

The Baloch Liberation Army (BLA), one of several insurgent groups battling the government, claimed responsibility for the attack.

BLA was also behind Balochistan's most widespread violence in years in August, when separatist militants attacked police stations, railway lines, and highways, killing more than 70 people.

Armed men also killed seven people last month when they stormed a residence housing laborers from Punjab.