Clashes broke out Friday as protesters led in convoys by cricketer-turned-politician Imran Khan and a populist cleric advanced on the Pakistani capital to try to topple the government they say was elected by fraud.

Clashes broke out Friday as protesters led in convoys by cricketer-turned-politician Imran Khan and a populist cleric advanced on the Pakistani capital to try to topple the government they say was elected by fraud.

Khan and preacher Tahir-ul-Qadri say the May 2013 general election that brought Prime Minister Nawaz Sharif to power in a landslide was rigged, and are demanding he resign and hold new polls.

They plan to rally in Islamabad to press their claims, at the end of a "long march" -- in reality a motorized cavalcade -- which set off Thursday from the eastern city of Lahore, around 300 kilometers (190 miles) away.

Police and witnesses said activists from Khan's Pakistan Tehreek-e-Insaaf (PTI) party clashed with supporters of Sharif's Pakistan Muslim League-N (PML-N) in the town of Gujranwala, some 200 kilometers (120 miles) southeast of Islamabad.

Khan said shots were fired on his march, telling ARY television news: "They threw stones at us while standing at police vans. They fired bullets at us."

However, police said there were no shots and an AFP photographer at the scene also heard no gunfire.

"Workers of PTI and PML-N clashed in Gujranwala and threw stones at each other," a police spokeswoman told AFP. "There was no firing incident."

The AFP photographer said a group of up to 40 youths who were following the convoy and shouting slogans clashed with workers from Khan's party before being dispersed by police.

Marvi Memon, a PMLN member of parliament and spokeswoman, told AFP the events in Gujranwala were "regrettable" but said there was no shooting and her party's workers had been provoked by what she called Khan and Qadri's "violent speeches".

Punjab Chief Minister Shahbaz Sharif, the premier's brother, ordered an investigation into the clashes and appealed for calm.

Supporters of PTI, which came third in last year's election, lined up to welcome the convoy in towns along the Grand Trunk Road which links Lahore and Islamabad.

Exact numbers on the march were difficult to judge, and more people are likely to join it as it passes through towns along the route, but Khan already hailed it a success.

"I can only see that the monarchy is nearing its end," Khan said, referring to Sharif.

"The people have decided as I had said that one million people will come to Islamabad, and they have come out."