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Thousands of protesters have gathered in Pakistan’s capital Islamabad after arriving in big convoys from Lahore.

Rally leaders Imran Khan and Tahirul Qadri demanded that Prime Minister Nawaz Sharif step down, alleging rigging in the 2013 elections.

Mr Qadri, an anti-government cleric, told his supporters in a midday speech to continue protesting until they bring a “peaceful revolution”.

Last year’s election saw the first civilian government transfer of power.

There was tight security in Islamabad as the protesters arrived in poor weather by truck, jeeps and cars after travelling the 350km (218 miles) from Lahore to Islamabad.

Cricketer-turned politician Imran Khan and cleric Tahirul Qadri, who have separate groups of supporters, have vowed to together bring one million followers on to the streets of the city.

Mr Khan, who heads the opposition Pakistan Tehreek-e-Insaaf party, said that the government was illegitimate, citing fraud and a failure to organise a probe into the elections.

Imran Khan was Pakistan’s most successful cricket captain before he entered politics in 1996

The government has condemned the opposition, saying a rally would not remove the prime minister

He called for new elections, vowing to continue a sit-in until Mr Sharif resigns.

Police estimated the crowd was 60,000 strong.

The BBC’s Shahzeb Jillani in Islamabad says that the numbers fall significantly short of the projected “million man march”, and that the real test of the crowd’s staying power is yet to come as Mr Khan’s stand-off is expected to drag on over the weekend.

His convoy of protesters was pelted with stones on the way, in the city of Gujranwala.

Officials from Mr Khan’s party said his vehicle was also shot at but he was not hurt.

A senior leader of Mr Sharif’s ruling Pakistan Muslim League party announced that the government was ready to investigate the allegations of fraud from last year’s elections, but said that Mr Sharif would not be removed through a rally.

The government says the protesters are trying to derail democracy. The prime minister’s spokesman Pervaiz Rashid condemned the “irresponsible behaviour and actions” of his opponents.

Mr Khan’s and cleric Tahirul Qadri’s supporters are angry about the sinking economy, growing militancy, and failure to deliver core services such as a steady electricity supply.