Suspected tribal militants in Pakistan's Balochistan province have blown up four electricity transmission towers, cutting power to a wide area.
The military has been fighting militants for months
A technician sent to repair the damage was then killed in an attack.
It came only hours after the provincial assembly voted to form a bipartisan panel to try to make peace between the authorities and warring tribal leaders.
Gas-rich Balochistan has seen months of violence as tribal groups push for greater political and economic rights.
The BBC's Zaffar Abbas in Islamabad says there seems to be no let-up in the violence in Balochistan.
Suspected tribal militants have been fighting the security forces there for nearly two years.
In the latest attack in Bolan, about 50km (30 miles) from the provincial capital Quetta, militants fired rockets to bring down four transmission towers supplying electricity to Kalat, Zhob and adjoining districts.
A team of technicians sent from Quetta to assess the damage was also attacked by militants, officials said.
One of the technicians was killed by a landmine and another seriously wounded.
Repair work was suspended as hundreds of workers belonging to the state-run water and power authority Wapda took to the streets in Quetta, demanding better security and protection.
About 80% of the province was left without power after the attack, officials said.
Suspected militants loyal to two powerful tribal leaders have previously been involved in attacking gas supply lines and blowing up railway tracks in the troubled province.
Earlier this week, Pakistan's President Pervez Musharraf again accused tribal leaders of putting up armed resistance to his plans to build a sea port and road network to turn Balochistan into a major trading zone.
But the Baloch tribal leaders say their struggle is for greater provincial autonomy and an increased share of mineral resources from the gas and oil rich province.
Thursday's move by opposition members in the Balochistan assembly to set up a bipartisan panel to broker a peace deal was surprising, our correspondent says.
Such attempts at ending the deadlock have previously failed because opposition parties had boycotted the officially appointed committees.
The latest move suggests that some Baloch opposition parties are now insisting on a negotiated settlement of the crisis, our correspondent says.