Imran Khan and Pakistani cleric begin protest marches in Islamabad

Two protest groups - one led by cricketer-turned-opposition politician Imran Khan, and the other by activist cleric Tahir ul-Qadri - are heading to the capital to demand that a government they condemn as corrupt steps down.

Both marches were initially banned but late on Wednesday the government said Khan's march could go ahead. On Thursday, police announced that Qadri could also march, despite previous calls for his arrest by the provincial government.

Khan and Qadri are not officially allied though both are sworn enemies of the government of Prime Minister Nawaz Sharif, whose party swept an election last year in the first transfer of power from one elected government to another in coup-prone Pakistan's history.

Muslim cleric Tahirul Qadri. (Photo: AP)

Qadri, a Muslim preacher turned political activist who usually lives in Canada, says he wants to see the government out by the end of the month. His supporters, many from a network of Islamic schools and charities, have been involved in several deadly clashes with police.

Qadri promises the country much if his movement triumphs.

"Every homeless person will be provided housing; every unemployed person will be given a job; low paid people will be provided with daily necessities," Qadri said in a speech on Thursday. One of Qadri's main complaints is that the killing of his supporters by police is not being properly investigated. About 2,000 of his supporters have been arrested, police say.

Last week, he called on his supporters to retaliate if attacked by police, raising fears of violence.

The protests and fears of clashes have fuelled tension in the country of 180-million people, beset by an Islamist militant insurgency, chronic power shortages and a sluggish economy. The political confrontation has revived concern about the central issue in Pakistani politics: competition for power between the military and civilian leaders.

Any threat to Pakistan's stability alarms its allies and neighbours, who fear rising religious intolerance and the Islamist militants who find refuge there. Some officials had accused elements within the powerful military of orchestrating the protests to weaken the civilian government. The military has declined to comment but has previously said it does not meddle in politics.

Many analysts doubt whether the military wants to seize power, but there is a widespread perception it could use the opportunity to put the civilian government under its thumb.

Despite those perceptions, Sharif is relying on the military for security in the face of the challenges. As a result, the government is likely less determined to pursue polices the military objects to, such as the prosecution on treason charges of former military leader Pervez Musharraf, analysts say. Khan said he was cheated in the general election in May last year and wants a proper investigation into his complaints.

His supporters were exuberant despite a huge traffic jam as they tried to set off on the 370-km (230-mile) journey to Islamabad on Thursday, an Independence Day holiday in Pakistan. Khan travelled in a modified, bulletproof shipping container with windows. Many of his supporters carried sleeping mats and food, determined to camp on Islamabad streets until their demands were met - including a demand for Sharif to resign.

"I was treated at his cancer hospital free of cost," said 50-year-old housewife Aasia Khan, referring to a charitable hospital that Khan set up in memory of his mother. "I owe him a lot and will support him until I die."

Khan's political ambitions were for years dismissed but he built up support, in particular among students. The one-time playboy cricket star developed a reputation as a conservative maverick and questioned Pakistan's close ties with the United States.

He won 34 seats in the 342-seat lower house of parliament in the last election. Sharif's party won 190 seats.