The attack, the second on electricity installations in Baluchistan in less than a week, was the latest in a series of assaults on state infrastructure in the southwestern province blamed on tribal rebels seeking greater autonomy.
The attackers blew up two electricity pylons late on Tuesday near Sibi district, about 100km southeast of provincial capital Quetta, suspending power to two thirds of the districts of Baluchistan province, including Quetta.
"The bombs were planted at the bases of the towers," said Jibrail Khan, a spokesman for Quetta Electric Supply Co, a state-run regional power utility, on Wednesday.
He said the authorities had restored electricity to parts of Quetta by using an alternate distribution system, but it would take at least two weeks to repair the damaged transmission line.
On Saturday, three power pylons were blown up in Nasirabad district, suspending supplies to surrounding areas.
Tuesday's attack came hours after a tribesman was killed when a bomb he was carrying exploded prematurely in Quetta. Two other people were wounded in the explosion.
Four more people were wounded when a bomb planted by suspected rebels exploded on a railway line leading out of Quetta, shattering windows on a passing train.
In January the gasfield at Sui
in Baluchistan was attacked
Baluchistan has been troubled for decades by a small-scale tribal insurgency, but recent attacks have been unusually intense in scale and frequency.
In the worst of the recent incidents, as many as 15 people died on 11 January, after tribesmen fired rockets at Pakistan's main gasfield at Sui, about 400km southeast of Quetta, cutting off supplies for more than a week.
Analysts have warned that the unrest in Baluchistan could explode into a full-scale uprising if not handled carefully.
The government rushed in extra troops to protect the vital gasfield after the 11 January attack and has not ruled out military action against tribesmen, but at the same time has said it is seeking a political solution to the crisis.