Supporters of Pakistan's cricketer-turned-politician Imran Khan wave their party flags at a rally in Islamabad, Pakistan, Saturday, Aug. 16, 2014. (B.K. Banagash/AP)

Tens of thousands of protesters thronged the streets of Pakistan’s capital Saturday, defying pouring rain to answer the call of a fiery cleric and a cricket- star-turned-politician, who are demanding that the government step down immediately.

Anti-government cleric Tahir-ul-Qadri and Pakistan’s most famous cricket player, Imran Khan, have led dual mass protests that have disrupted life across Islamabad. They are demanding that Prime Minister Nawaz Sharif step down over alleged fraud in the country’s May 2013 election, something Sharif has refused to do.

The protesters have vowed to remain in the streets until Sharif leaves office, raising fears of political instability in the nuclear-armed nation, where the democratic transfer of power took place for the first time just last year. While the crowds have fallen well short of the million marchers that both men promised, their presence and the government’s heightened security measures have virtually shut down business in the capital.

On Saturday, Qadri told his supporters to continue protesting until they bring about a “peaceful revolution.”

“Nawaz Sharif should be arrested when he steps down and he should not be allowed to leave the country,” he said. He also called for the dissolution of Parliament and fresh elections.

Supporters of cleric Tahir-ul-Qadri wave flags at an anti-government rally in Islamabad on August 16, 2014. (Asif Hassan/AFP/Getty Images)

Sharif has given no indication that he intends to step down, and leaders of his party said Qadri’s demands were unconstitutional.

Khan, whose camp is parallel to Qadri’s on the city’s eastern edge, also vowed Saturday to continue his protest until Sharif steps down. He called on more people to join him.

“A new history is going to be recorded in Islamabad,” Khan told the protesters.

Khan and Qadri each vowed to bring 1 million followers into the streets of Islamabad, a city of about 1.7 million inhabitants. But police Saturday estimated that nearly 35,000 people were present at Qadri’s rally and 25,000 at Khan’s.

The two men have maintained a separation between their rallies, although both have the same goal and both traveled to Islamabad from the eastern city of Lahore. Khan’s crowd on Saturday reflected his popularity among Pakistan’s youth, many of whom have been looking for a new political leader after decades of tight control by either the military or the country’s two longtime political parties.

Groups of young people danced to music and songs while waving political and Pakistani flags. Khan helms the Pakistan Tehreek-e-Insaf party, which is the third-largest political bloc in Parliament.

Over at Qadri’s protest, just yards away, the mood was more somber and organized, reflecting the cleric’s religious roots. Qadri draws his popularity from his network of mosques and religious schools across the country. Last year, Qadri, who is also a Canadian national, held a protest in the capital calling for vaguely worded election reforms ahead of the country’s May poll, bringing life in Islamabad to a halt.

Shortly after Qadri’s speech, senior cabinet minister Ahsan Iqbal urged the two opposition leaders to step back from their demands.

“We do hope that Imran Khan and Tahir-ul-Qadri will show flexibility” to end the political instability, Iqbal said.

Ahead of the protests, security forces put shipping containers on streets as roadblocks and stationed riot police around the capital.

Sharif was himself overthrown in the 1999 coup that brought former army chief Pervez Musharraf to power.

— Associated Press