A car lost control and hit a line of vehicles behind Samajwadi Party chief Akhilesh Yadav's convoy in Uttar Pradesh's Hardoi district, the police said.
No vehicle in the convoy was affected and Mr Yadav was driven to his destination safely, a police officer said. He had gone to attend a programme.
Three people were injured. They were taken to a local hospital, where doctors said the injuries are minor.
"It happened suddenly. We don't know how the accident happened. Some seven-eight cars were involved in the accident," Naseem, one of the three injured people, told reporters in hospital.
More than seven cars were damaged in the accident on the expressway just after Farhat Nagar, 100 km from state capital Lucknow.
"The vehicles were driving fast behind Akhilesh Yadav's convoy. One of them lost control and hit other vehicles," Hardoi police officer Anil Kumar Yadav said.