Police clash with supporters of an opposition leader, Muhammad Tahir-ul-Qadri, in Islamabad. Qadri is a religious scholar and progressive politician. (Reuters)

A leading opposition figure returned to Pakistan on Monday, resulting in chaos at two major Pakistani airports and posing a new challenge to Prime Minister Nawaz Sharif’s efforts to keep his grip on power.

Muhammad Tahir-ul-Qadri, a religious scholar and moderate politician, said he was returning from exile in Canada to lead a “democratic revolution” against Sharif’s government just a year after the prime minister regained power. Qadri said Sharif has not done enough to implement electoral and social-justice reforms and has been too timid in his approach to the Pakistani Taliban.

“I will soon call for a movement to usher in revolution in the country,” said Qadri, leader of the Pakistan Awami Tehreek (PAT) party, when he arrived in Lahore. “This government will be toppled. . . . I will lead the revolution, and I will be the one in charge to ensure that these terrorists, these killers and corrupt rulers are punished.”

Despite his fiery rhetoric, analysts are skeptical that Qadri poses an imminent threat to the government.

Sharif, who previously served two terms as premier before he was ousted in a military coup in 1999, was sworn in last June after his Pakistan Muslim League-N party won the most seats in parliamentary elections in the spring.

But Qadri commands a loyal group of followers and is said to have close ties to the Pakistani military.

Rasul Bux Rais, an Islamabad-based political science professor and analyst, said Qadri’s return is another sign that a rift may be emerging between Sharif and the country’s powerful military leadership. Many former military commanders say army chiefs were eager to launch a military offensive against the Pakistani Taliban this past winter. But Sharif authorized the operation only 10 days ago, after Taliban militants stormed Karachi’s international airport, killing 26 security personnel and civilians.

“I don’t think the military has written off Nawaz Sharif, but they will use these tactics to put pressure on him,” Rais said.

Although Qadri announced his planned return weeks ago, his arrival Monday created hours of tension in the capital, Islamabad, and in Lahore, Pakistan’s second-largest city.

Last week, as news spread that his return was imminent, a bloody clash erupted outside his house in Lahore when his supporters attempted to stop police from removing security barriers there. Fearing more violence, Sharif’s government went to extraordinary lengths to try to keep Qadri supporters from greeting him at Islamabad’s international airport.

Shipping containers were used to block the highway leading to the airport, and demonstrations were banned in the capital and the adjoining city of Rawalpindi. But thousands of Qadri supporters showed up anyway and clashed with police for hours, leaving more than 70 officers injured, officials said.

The disturbance, which closed the airport for 10 hours, caused officials to order that Qadri’s Emirates flight be diverted to Lahore.

Once the plane landed, however, Qadri refused to get off, insisting that he should have been allowed to land in Islamabad. He also said he feared for his safety and would disembark only when no police or government officials were in the airport area.

“I will not leave this plane [until] a representative of Pakistan’s army comes and talks to me,” Qadri said.

The five-hour standoff ended at about 2 p.m. when the governor of Pakistan’s Punjab province, Chaudhry Muhammad Sarwar, guaranteed Qadri’s security.

Ayaz Amir, a columnist and former member of Parliament, said the drama surrounding Qadri’s return made the national government appear weak. “The message that comes out from this is the thing that can control this situation is the army,” he said.

It was not the first time Qadri has come back to Pakistan and stirred tension with national leaders. After going into exile in 2007, citing death threats from the Taliban, he returned in 2012 and announced plans to overthrow Asif Ali Zardari, then Pakistan’s president.

Qadri organized what he called a “million man” march in Islamabad against the Pakistan Peoples Party, and his followers staged a four-day sit-in in the capital. To resolve the standoff, Zardari agreed to implement reforms if Qadri would return to Canada.

Qadri says he is back in Pakistan now because those promises have not been fulfilled.