The attack on his convoy in Punjab on Thursday, apparently by a lone gunman, killed one man and wounded at least 10 others. It significantly raised the stakes in the political crisis that has gripped the country since Mr Khan was ousted as prime minster in April.
Mr Khan is now in a stable condition. He and his supporters have called it an attempted assassination.
He escaped with at least one bullet wound to his right leg when a gunmen repeatedly fired a pistol at a modified container lorry as it drove slowly through a thick crowd in Wazirabad, about 170 kilometres east of Islamabad.
"Everyone who was standing in the very front row got hit," former information minister Fawad Chaudhry, who was standing behind Mr Khan, told AFP.
A close aide and spokesman for his political party, Pakistan Tehreek-e-Insaf said in a video message that Mr Sharif, Interior Minister Rana Sanaullah and Maj Gen Faisal Naseer were behind the shooting.
Asad Umar said his party was calling for the immediate removal of the officials from office but offered no evidence to back his claim that they were involved.
The former prime minister was leading a march toward the capital Islamabad to demand early elections.
Supporters have taken to the streets across different cities to protest and Mr Khan’s party leaders are calling for the march to continue on Friday.
Mr Sharif’s government rejected the accusation that it was behind the attack. It has condemned the incident and called for an investigation.
PTI officials are expected to meet on Friday to discuss the immediate fate of Mr Khan's campaign march, and vowed it would continue.
"The real freedom long march will continue and the movement for people's rights will remain until an announcement on the general elections," an official said on Twitter.