Clashes in Pakistan after shots fired at opposition leader Imran Khan

Clashes broke out Friday as tens of thousands of Pakistani protesters from two anti-government movements converged on the capital, presenting the 15-month-old civilian government with its biggest challenge yet.

Gunshots hit the vehicle of former cricket star and opposition politician Imran Khan as he led his supporters through the eastern city of Gujranwala. The convoy, which was not bullet-proof, was pelted by a stone-throwing mob, apparently consisting of workers loyal to the ruling Pakistan Muslim League (PML-N) party, Khan told Al Jazeera. He said police watched without intervening.

Pervez Rashid, the federal information minister and a ruling PML-N party leader, said it was an unfortunate incident.

"We know that incidents like these lead to conflict between political leaders, and it causes much harm. We are going to try our hardest through our [parliamentarians] and local administration to convince [our local party workers] to approach the situation with patience, even if they are angered," he told a local television news channel.

Television pictures showed people tearing up posters featuring Khan's party, Pakistan Tehreek-i-Insaf (PTI), and clashing with his supporters.

Khan and populist cleric Tahir ul-Qadri are slowly leading separate processions towards Islamabad, where they plan to occupy main streets until Prime Minister Nawaz Sharif resigns. Khan is protesting against alleged electoral irregularities in last year's polls. Qadri has accused police of killing 22 of his supporters during clashes in the eastern city of Lahore in June and this month. Police confirmed 11 deaths.

Security was tight in the capital and authorities blocked several main roads with shipping containers and barbed wire in an effort to thwart the marches. Riot police were out in force but hundreds of protesters began to gather, banging drums, singing and dancing as they prepared to welcome their colleagues approaching the city.

"We have come to save our country because of the call of our leader, Imran Khan," said 36-year-old Ajaz Khan in central Islamabad. He was speaking before the shots were fired at Khan.

"We will not leave from here until our leader tells us to go," he said.

Speaking at an Independence Day ceremony in southwestern Pakistan, Sharif criticized the rally, calling it "negative politics." Sharif said Khan would be better advised to "work to alleviate poverty and improve law and order" in Pakistan.

The protests have raised questions over stability at a time when the nuclear-armed nation of 180 million is fighting an offensive against Pakistani Taliban militants and the influence of anti-Western and sectarian groups is growing.

In the latest violence, 10 militants were killed and 13 members of the security forces were wounded in attacks on two air force bases in Quetta late on Thursday, the third time since June that airports have been targeted.

The government is also struggling to overcome daily power shortages, high unemployment, and spiraling crime — the legacy of decades of corruption and neglect. Anger over the economy means the protests appeal to many disillusioned young Pakistanis.

Some members of Sharif's ruling party have suggested the protests are secretly backed by elements in the powerful military, which has had an uneasy relationship with Sharif. While few people think there will be a coup, many officials fear the threat of unrest will increase the military's hold over the government.

The military has been frustrated with the government, in particular over the prosecution of former army chief and president Pervez Musharraf for treason.

There was also disagreement between the government and the army on how to handle the Pakistani Taliban, with the army favoring military action and the government holding out hope for peace talks.

Most observers expect the military to play referee, to maintain security but not support action to force Sharif out.

"Imran will not get from the army what he was expecting," said an analyst close to the military. "If there was any confusion earlier about whether the army would help Imran or rescue him or topple the government, there should be none now. There is no question of army intervention."

Al Jazeera and wire services