Nine others were hurt. Mr Khan was hit in the leg, but escaped serious harm, party official Asad Umar said.
A suspect was immediately arrested at the scene and police later released a video of him in custody, allegedly confessing to the shooting and saying he acted alone. It was not clear under what conditions he made his statement.
“Only Imran Khan was my target,” said the suspect, identified as Faisal Butt by information minister Maryam Aurangzeb. The attack has raised fresh concerns about growing political instability in Pakistan since Mr Khan’s ousting in a no-confidence vote in Parliament in April.
Since then, he has mobilised mass rallies across the nuclear-armed nation of 225 million, whipping up crowds with claims he was a victim of a conspiracy by his successor, Prime Minister Shahbaz Sharif, and the US. Both the new premier and Washington have denied the allegations.
Pakistan has a decades-long history of political assassinations, including that of Benazir Bhutto, the first democratically elected female leader of a Muslim country, in 2007. Mr Khan was later seen with a bandage on his right leg, just above the foot, according to reports and a blurry image. He was moved to another vehicle from his truck, from which announcements were being made that he was safe.
“He is being taken to a hospital in Lahore, but he is not seriously wounded – a bullet hit him in the leg,” Asad Umar, an official from Khan’s Tehreek-e-Insaf party, told reporters. The Interior Ministry said the government has ordered an investigation.
The attack happened in the Wazirabad district in the eastern Punjab province where the former cricket star turned Islamist politician was travelling in a large convoy of trucks and cars heading toward the capital of Islamabad. The convoy is part of his campaign aimed at forcing the government to hold early elections.
District police officer Ghazanfar Ali said one person was killed and nine others were hurt in the attack.
Among the wounded was Faisal Javed, a politician from Tehreek-e-Insaf. In a video statement, with bloodstained clothes, he said the attack would not stop Mr Khan’s protest march to Islamabad. Interior Minister Rana Sanaullah Khan condemned the attack.
Fawad Chaudhry, a senior leader from Mr Khan’s party, told supporters surrounding Mr Khan’s truck the attack was an attempt to kill the former premier. Mr Khan has been at loggerheads with Pakistan’s powerful military and has refused to halt his plans to march on the capital.
The military has said although Mr Khan had a democratic right to hold a rally in Islamabad, no one would be allowed to destabilise the country. Authorities in Islamabad have already deployed additional security around the city to deter any clashes or violence.
The attack came less than a week after Mr Khan began his march from Lahore, the capital of Punjab province, with thousands of supporters.
Earlier, Mr Chaudhry had said they planned to enter Islamabad on Friday.
Mr Sharif’s government has said there will be no early election and the next balloting will be held as scheduled in 2023.