Mr. Khan, who was leading a protest march, was wounded in both legs, in an attack that threated to plunge the country into turmoil.
ISLAMABAD, Pakistan — Former Prime Minister Imran Khan of Pakistan was wounded at a rally on Thursday after at least one unidentified man opened fire on his convoy, in what aides have called a targeted attack.
The attack, one of the most serious outbreaks of political violence targeting a prominent government official since former Prime Minister Benazir Bhutto was assassinated in 2007, hit while Mr. Khan was in Wazirabad, in eastern Pakistan, leading a protest march to the capital, Islamabad.
Mr. Khan, 70, sustained bullet wounds in both legs and was moved to Lahore for treatment, officials said. Fawad Chaudhry, a senior member of Mr. Khan’s party, Pakistan Tehreek-e-Insaf or P.T.I., called the shooting “100 percent an assassination attempt.”
A video of the attack showed Mr. Khan standing with his aides in a container mounted on top of a truck as it moved slowly through a crowd of his supporters. As gunshots rang out, Mr. Khan and others on the truck appeared to duck down.
Dr. Faisal Sultan, the former health minister who treated Mr. Khan, said at a news conference Thursday evening that Mr. Khan was in stable condition. Seven people including Mr. Khan were injured in the attack and one person died, according to Waqas Nazeer, the spokesman for the Punjab Police. One suspect has been detained, he added.
The outburst of political violence comes at a moment of intense acrimony in Pakistan. Mr. Khan was removed from office in April in a vote of no confidence after falling out with the country’s top military leaders, who are widely considered to be the invisible hand guiding Pakistani politics.
Mr. Khan claimed that the vote was part of a conspiracy by the country’s military establishment and his political opponents to oust him from power. And in the months since, the former cricket star turned politician has made a stunning comeback, drawing thousands to his rallies across Pakistan.
In impassioned speeches, he has cast himself as a martyr to the domineering presence of the military in Pakistani politics and the insidious influence of corrupt politicians, tapping into deep-seated frustrated among Pakistanis over the country’s political troubles.
And on Thursday, bloodied from bullet wounds, Mr. Khan embodied that persona for hundreds of thousands of his supporters across the country, setting off pointed accusations of blame that threaten to ignite Pakistan’s political tinderbox and plunge the country into turmoil.
Even before the shots were fired, the country’s political atmosphere was rife with personal attacks and at times violence. In recent months, as Mr. Khan’s popularity has grown, so, too, has a crackdown on the populist leader and his supporters who have been imprisoned and intimidated. Mr. Khan has also faced mounting cases against him in court, and last month, Pakistan’s election commission disqualified him from completing his current term in Parliament.
The cases against him are seen by his supporters and many political analysts as part of a coordinated campaign by the Pakistani authorities to sideline him from politics — an accusation that the Pakistani military and political leaders have repeatedly denied. But even so, the crackdown has only buoyed his popularity, analysts say, and Mr. Khan has demonstrated a unique ability to elude Pakistan’s typical playbook for marginalizing political leaders.
In a show of political strength, last week Mr. Khan and his supporters set off on a highly anticipated dayslong march to Islamabad from Lahore in an effort to pressure the government to hold general elections sooner than August, when they are scheduled to happen.
Javed Mustafa, a P.T.I. supporter, said he had been walking with the convoy since Friday, joining thousands of others around 11 a.m. each day and marching until late into the evening. When the attack took place on Thursday, chaos broke out in the crowd, he said.
“I was marching far behind but suddenly heard some gunshots and then a stampede followed,” said Mr. Mustafa, 29, who recently graduated in computer science from a university in Lahore.
In a video released by the police to local television stations after the attack, a young man who appears to be in custody says that he wanted to kill Mr. Khan and that he had acted alone.
“Imran Khan was leading people astray,” the man said. “I could not tolerate this. That is why I tried to kill him. I only tried to kill Imran Khan and no one else.” The New York Times was unable to independently verify the video or the man’s identity.
At least one senior aide to Mr. Khan, Sen. Faisal Javed Khan, was among those wounded in the attack, according to local news media. Photographs circulating on social media showed the aide, who often helps rally crowds at the former prime minister’s protests, dressed in white and splattered with blood. He did not appear to be seriously injured.
Prime Minister Shehbaz Sharif immediately condemned the attack and requested a report on it from the country’s Interior Ministry.
“We pray for the speedy recovery of Imran and others injured,” he said in a statement. “Violence should have no place in politics.”
P.T.I. party leaders have pledged that Mr. Khan’s so-called “Long March” to Islamabad will return to the streets after Mr. Khan has recovered from the attack.
Moments after the shooting, Mr. Khan’s aide, Mr. Chaudhry, gave an impassioned speech to P.T.I. supporters.
“I urge all P.T.I. supporters across Pakistan to avenge the attack on Imran Khan,” he shouted. “Our party is a peaceful party. But our leader was attacked with guns.”
A close aide to Imran Khan, Asad Umar, released a video statement accusing the prime minister, interior minister and a senior official in Pakistan’s intelligence services of orchestrating the attack. The statement doubled down on Mr. Khan’s recent political rhetoric that had centered on the idea that powerful people in the government are conspiring to remove him from politics.
On Thursday evening in several major cities, P.T.I. supporters poured into the streets and blocked major roads to show their anger over the attack. In Karachi, protesters in several neighborhoods and burned tires, causing massive traffic jams.
“Imran Khan is fighting with the existing, powerful system not for himself but for future generations,” said Inayat Khattak, a party’s leader, who led a protest in Karachi. “Now it is the time for everyone in the country to stand with Mr. Khan.”
Salman Masood reported from Islamabad, and Christina Goldbaum from Kandahar, Afghanistan. Zia ur-Rehman contributed reporting from Karachi and Ihsanullah Tipu Mehsud from Islamabad.