Former Pakistan PM leads protest march on blockaded Islamabad

Since being removed from power through a no-confidence vote last month, the cricket star turned politician has heaped pressure on the country's fragile new coalition rulers by staging mass rallies, touting a claim he was turned out from office in a "foreign conspiracy".

In a centrepiece showdown with his rivals, Khan had called for supporters of his Pakistan Tehreek-e-Insaf (PTI) party to gather in Islamabad and stage a sit-in until fresh elections are called.

"No obstacle can stop us, we will cross all the barriers and will reach... Islamabad," Khan declared, flanked by more than 20,000 supporters.

The government headed by Prime Minister Shehbaz Sharif has pledged to stop the convoy from entering the city, calling the rally an attempt to "divide the nation and promote chaos".

All major roads surrounding Islamabad, where a heavy security presence is in place, were blocked off with shipping containers while entry and exit points of major nearby cities were also cut off.

Sporadic clashes broke out between police and protesters who have tried to clear the roads, with tear gas fired in several cities.

Khan joined the march in dramatic fashion, arriving in a helicopter that touched down on a motorway clogged with supporters outside the city of Mardan, 100 kilometres (62 miles) northwest of Islamabad.

The convoy later crossed a bridge that straddles PTI-run Khyber Pakhtunkhwa province and government-run Punjab province, where shipping containers blocking the route were pushed to the side of the road by protesters.

"When we reached here, we had a tough clash with the police. But they fled and we were able to clear the bridge for Imran Khan," said Zulfiqar Khan, a 42 year-old labourer, in Attock.