Former Pakistan Prime Minister Imran Khan was shot in the shin on Thursday when his anti-government protest convoy came under attack in the east of the country.
Several others in the convoy were wounded and the information minister said a suspect had been arrested.
One party member said there were reports one person had been killed.
"It was a clear assassination attempt. Khan was hit but he’s stable. There was a lot of bleeding," Fawad Chaudhry, a spokesperson for Khan's Pakistan Tehreek-e-Insaf (PTI) party, told Reuters.
"If the shooter had not been stopped by people there, the entire PTI leadership would have been wiped out."
Local media showed pictures of Khan, 70, waving to the crowd after being evacuated from his vehicle following the shooting.
He was taken to hospital in Lahore after the attack in Wazirabad, nearly 200 km (120 miles) from the capital, Islamabad.
Protesters poured out on to streets in some parts of the country as PTI leaders demanded justice.
Imran Khan was shot in the leg but was stable while being taken to hospital. He waived at supporters too. #عمران_خان_ہماری_ریڈ_لائن_ہے pic.twitter.com/XizoAQzPax
— PTI (@PTIofficial) November 3, 2022
Former cricketer Khan was leading a protest march on Islamabad to demand snap elections. There were hundreds of people in the convoy.
Prime Minister Shehbaz Sharif condemned the shooting and ordered the interior minister to seek an immediate investigation.
Since being ousted in April through a parliamentary vote, Khan has held rallies across Pakistan, stirring opposition against a government that is struggling to bring the economy out of the crisis that Khan's administration left it in.
Khan had planned to lead the motorised caravan slowly northwards up the Grand Trunk Road to Islamabad, drawing more support along the way before entering the capital.
"I want that all of you participate. This is not for politics or personal gain, or to topple the government... this is to bring genuine freedom to the country," Khan said in a video message on the eve of the march.