Police officers and other officials in Pakistan's Punjab province have been suspended by chief minister Chaudhry Pervaiz Elahi for leaking the suspected attacker's confessional statement after the gun attack on former prime minister Imran Khan.

Khan, 70, sustained a bullet injury on his leg when a gunman opened fire on Thursday on the container-mounted truck carrying him during his protest march, killing one person, but the former Pakistan prime minister was out of danger in what his party claimed was an "assassination attempt."

Punjab Chief Minister Chaudhry Pervaiz Elahi has taken notice of leaking the suspected attacker's confessional statement after the gun attack on Pakistan Tehreek-e-Insaf (PTI) chief Imran Khan during the long march, ARY News reported on Thursday.

Elahi ordered Inspector General (IG) Punjab police to take disciplinary action against the irresponsible officials. After the leaking of the suspect's confessional statement, the Station House Officer (SHO) and other officials of the concerned police station were suspended, the report added.

The chief minister said in a statement that all mobile phones of the police station's staffers were confiscated and they will be sent for a forensic audit.

Elahi issued directives to hold an inquiry into the incident of the video leak of the suspected attacker. He directed IG Punjab to begin a probe to ascertain the motives of the gun attack.

The directives were issued in an emergency session chaired by the Punjab Chief Minister on Thursday.

The assailant, who opened fire at Khan during the party's long march, has confessed to the crime, saying that the former premier was his only target.

In a video statement available with ARY News, the attacker said he was planning the assassination attempt ever since Imran left Lahore. "I tried my best to kill him. I wanted to kill Imran Khan only and no one else," he added.

The incident occurred near Allahwala Chowk of Wazirabad town in Punjab when Khan was leading the long march to Islamabad demanding early elections.

Asad Umar, the senior leader of Khan's Pakistan Tehreek-e-Insaf (PTI) party, told the media that a bullet hit Khan's leg.

Khan underwent surgery at Shaukat Khanum Hospital in Lahore and his condition is stable, his party leader Omar Ayub Khan said.