Islamabad tightens security as Imran Khan-led protest intensifies

Security has been further tightened in the 'secure zone' of Pakistan's capital Islamabad after protest leader Imran Khan's Pakistan Tehreek-i-Insaaf (PTI) party called on marchers to enter the zone.

The government has forbidden protesters from breaching the highly secure so-called red zone housing key state buildings and foreign embassies, even as thousands of anti-government protesters are occupying two Islamabad highways.

On Monday MPs from the former cricketing great's PTI vowed to quit their national assembly seats.

The PTI has 34 of the national assembly's 342 seats, making it the second-biggest opposition group.

The party said it would also resign from both the national assembly and provincial assemblies, except for Khyber Pakhtunkhwa province, which it governs. But no resignations have been submitted so far.

Imran Khan along with thousands of his supporters has been protesting in the capital since Friday demanding the government's resignation.

He accuses Prime Minister Nawaz Sharif's PML-N party of vote-rigging in the 2013 election and has called on him to stand down.

Sharif won that election by a landslide in what was Pakistan's first peaceful transfer of power between two civilian democratic governments.

The government has accused the protesters of attempting to derail democracy. It has offered talks on their concerns, but these have been rejected.

Along with Khan, anti-government cleric Tahirul Qadri mobilised supporters to march on Islamabad and they are camped out in the city.

Security around the red zone has been massively increased, correspondents say, with more police and paramilitary troops deployed there.

Imran Khan has spent the night in a shipping container at the site of the sit-in but he tweeted on Tuesday that he would lead the march into the red zone, calling it a "defining moment" for Pakistan.

But other opposition figures have criticised the demonstrations and Khan's call for people to stop paying tax bills in protest against the government.