Moazzam Ali Jatoi, an official with the Levies Force, which serves as police and paramilitary in the area, said the attack took place near the Machh coal field, about 48 kilometres (30 miles) east of the provincial capital Quetta.
Picture shown is for illustrative purposes only.
Ethnic Hazara make up most of the Shiite population in Quetta, the capital of Balochistan — the country's largest and poorest region, rife with ethnic, sectarian and separatist insurgencies.
They are often targeted by Sunni militants, who consider them heretics, though it was unclear why the attackers targeted the coal mine specifically.
The attack, before dawn on Sunday, took place in the far-flung and mountainous Machh area while the miners slept, Durrani said, adding that four other miners were injured and were being treated at the local hospital.
A security official told AFP the attackers first separated the miners, tied their hands and feet, took them out into the hills and later killed them.
Both Durrani and the security official said the victims belonged to the Hazara community.
Durrani said the mine was deep in the mountains.
It was not clear how exactly the miners were killed, he told the media.
The assailants fled after the attack. Both officials said police and members of the local paramilitary force were on the scene, where a search operation had been launched to trace the attackers.
No group has claimed responsibility.
In a tweet, Prime Minister Imran Khan condemned "the killing of 11 innocent coal miners in Machh" as a "cowardly inhumane act of terrorism".
Liaqat Shahwani, a spokesman for the provincial government, confirmed the incident and told private TV channel Geo that it was an act of terrorism.
Though Pakistan's mines are notorious for poor safety standards, such attacks against miners are rare.