( CNN ) -- Thousands of anti-government supporters led by two of Pakistan 's most influential figures have joined a march to Islamabad to demand the resignation of the country 's prime minister , prompting a major security operation . By early Friday , an estimated 15,000-20,000 people had joined cricketer-turned-politician Imran Khan on the outskirts of Lahore in Pakistan 's northwestern Punjab region . The procession took to the roads in cars , trucks and buses to make the 230-mile ( 370-kilometer ) journey to the capital . The march started on Thursday as Pakistan celebrated Independence Day . Khan , the former Pakistan cricket captain and leader of the Tehreek-e-insaaf ( PTI ) political party , has called on Prime Minister Nawaz Sharif to stand down amid claims of vote rigging during last year 's election , a claim Sharif has rejected . 'Huge security operation ' The huge convoy was joined by followers of outspoken cleric Tahir ul Qadri , who called on his supporters to join what he described as a `` revolution march . '' Qadri , who led protests against Pakistan 's government last year that brought the capital to a standstill , has accused the Sharif government of corruption and campaigned for more to be done for the country 's poor . The march , which has been peaceful so far , prompted a huge security operation across the country , with tens of thousands of soldiers and police deployed along the route to Islamabad , while massive shipping containers and reels of barbed wire have been used to seal off many roads and highways . However , many Qadri supporters joined the march armed with sticks and improvised shields . Last week , at least five of his supporters were killed during clashes with security forces in the country 's northwestern Punjab province . Capital gathering . Organizers from both camps expect thousands more to join the procession as they get closer to the capital . A Khan representative told CNN Thursday that they anticipated around 100,000 people would be taking part . They are expected to assemble in central Islamabad , where security has been especially tight , with routes to many government buildings and embassies blocked by containers and guarded by army personnel , who assumed responsibility for the city 's security . Late Thursday , the country 's interior minister Chaudhry Nisar Ali Khan told a press conference that the government had officially permitted the march to go ahead on the condition that protesters do n't cross into the capital 's `` red zone '' -- a tightly controlled area containing many government buildings . So far , crowds in the capital have been small , but they 're expected to increase significantly as the march draws nearer later Friday . On Wednesday , in a rare address to the country , Prime Minister Sharif refuted accusations of electoral rigging and stressed that Pakistan has moved forward over the past 14 months in terms of `` currency value , foreign investment and economic growth . '' In an apparent attempt to appease Khan 's demands for an investigation into electoral fraud last year , Sharif offered to form a commission consisting of three Supreme Court judges to investigate the claims . But at a press conference shortly after the prime minister 's address , Khan said the government 's response had arrived too late in the day and that he was now officially calling for the resignation of Sharif . The political instability comes at a time when Pakistan is waging a bloody war against militants -- particularly in the restive tribal regions along its border in Afghanistan . On Thursday two airbases in the southwestern city of Quetta in Balochistan Province were attacked by insurgent gunmen wearing suicide vests . But by early Friday , security forces repelled the attack , killing 10 terrorists and capturing another five , according to Imran Qureshi , the Superintendent of police in the city . There was no immediate claim of responsibility for the attack . But , senior police officers suspect Islamist militants could be behind the two coordinated attacks . Sarfaraz Bugti , the Home Minister Balochistan , told CNN the dead gunmen were Uzbeks . Journalist Syed Ali Shah contributed to this report .
Supporters of ex - president Imran Khan and cleric Sheikh ul Islam join march to capital . Organizers invite people to join as they near Lahore . The march has been peaceful so far , with thousands of police deployed along the route . The political instability comes as Pakistan fights a bloody insurgency .