Police fired teargas shells and used batons to evict thousands of people squatting on a highway linking the capital Dhaka with the port city of Chittagong on Friday.
They protesters are demanding adequate power supplies to run their irrigation pumps.
A witness said a local legislator, Mohammad Slahuddin, tried to persuade the protesters to end their sit-in on the highway, but he was jeered away.
A police officer said "the people have just gone wild and are attacking anyone coming on their way".
The violence spread when activists of the ruling Bangladesh Nationalist Party (BNP) began sporadic attacks on the protesters, witnesses said.
They said an unspecified number of vehicles including several buses were damaged in stone-throwing.
"It is not often possible to restore order when everyone turns unruly"
Authorities have largely withdrawn police from the spot, apparently so as not to provoke the protesters.
Another police officer said that "it is not often possible to restore order when everyone turns unruly".
"We hope the situation will gradually calm down by nightfall," he said.
Most areas in Bangladesh including Dhaka remain without electricity for several hours a day.
There is also a shortage of clean drinking water in the capital, a city of 10 million people, and most other parts of the country.
At least 20 people have been killed this year in clashes with police in the northwestern area of Kanshat which has emerged as a focal point of the protests against power shortages.
An official of the state-owned Power Development Board said 25 of Bangladesh's 60 power stations were out of operation because of faults.