By M Ilyas Khan
BBC News, Karachi
More protests have been held overnight in Pakistan's biggest city, Karachi, over continued power cuts.
Anger at the lack of electricity has spilled over into the streets
Demonstrators lit bonfires on main streets in the southern city causing huge traffic jams, eyewitnesses said.
A shortage of hundreds of megawatts of power has hit large parts of Pakistan since the onset of the summer heat, causing riots and violence.
Karachi, the country's financial capital and a city of 14 million people, is the worst affected.
Power cuts, sometimes for as long as 12 to 16 hours a day, have caused widespread disruption to life in the city and much anger.
Traders and manufacturers in Karachi say they are losing millions of dollars a day in lost business because of the repeated cuts.
Angry protesters blocked main streets in the commercial district of Saddar in central Karachi on Monday night, choking up traffic on main connecting routes.
In the Liaquatabad neighbourhood, also in central Karachi, demonstrators set tyres on fire and blocked the road, severing eastern parts from western Karachi.
Thousands of vehicles were stuck in traffic jams for several hours.
"It took me three hours to drive from Saddar to my home in the Garden area, normally a 15-minute drive," says Amin Qureshi, a bank executive.
Cloth merchant Rehan Ali said the number of customers had dwindled due to repeated power breakdowns.
"There is no business at the shop, and no peace at home," he told the BBC.
A spokesman for the Karachi Electric Supply Corporation (Kesc), Sultan Ahmad, said power demand in Karachi, where temperatures have been reaching 40C, had exceeded the supply by about 300 megawatts.
He also blamed frequent breakdown in Kesc's aging distribution network for the power crisis.