Local security officials said the militants blew up the 16-inch diameter gas pipeline in the Dera Bugti District of Balochistan on Monday.
The gas supply to hundreds of consumers in several towns across the troubled region has been suspended as a result of the blast.
The assailants later fled the scene and their whereabouts still remain unknown.
There was no immediate claim of responsibility for the attack.
Law enforcement forces cordoned off the area after the incident, and launched an investigation.
Pro-Taliban militants and some Baloch insurgent groups often carry out attacks against security forces as well as civilians and have managed to spread their influence in various regions of the country despite frequent offensives by the Pakistani army.
A number of Baloch militant groups say they want greater political autonomy and a share of the province’s natural resources.
Pro-Taliban Militants have carried out numerous attacks against security forces as well as civilians since 2001 when Pakistan entered an alliance with the US on the so-called war on terror.
Pakistani government has said it will use an all-out military action as a last resort to address the issues of extremism and militancy in the country.
Thousands of Pakistanis have lost their lives in bombings and other militant attacks since 2001, when Pakistan entered an alliance with the US in the so-called war on terror.