The bus was taking family members back to their village after a wedding party in the town of Dadu in the southern province of Sindh when it struck the power lines.
"The bus immediately caught fire after an iron box on its roof hit the high-tension wire, killing 11 people and injuring 14 others," a senior local police official Irfan Baloch told AFP.
Four women and three children were among those killed.
Police and rescue officials along with local villagers struggled to save the injured from the fire, who were shifted to hospital.
Prime Minister Nawaz Sharif expressed sorrow over the deaths of the passengers and directed the authorities to provide medical assistance to the injured.
On April 10, five people including two children were killed in car-motorcycle collision near Shahdadkot.
Read: 2 children among 5 killed in road accident in Sindh
Pakistan has an appalling record of fatal traffic accidents due to poor roads, badly-maintained vehicles and reckless driving.
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