Thousands of anti-government protesters gathered in the Pakistani capital late Friday as two large anti-government groups arrived to stage protests aimed at unseating the government of Prime Minister Nawaz Sharif.
The protests in Islamabad led by opposition leader Imran Khan and Muslim cleric Tahir ul-Qadri constitute the biggest challenge yet to Sharif's year-old government.
Khan and Qadri say the government is corrupt. Their two movements are not officially allied.
Earlier Friday, clashes broke out in the city of Gujranwala after gunshots were fired at Khan's vehicle as he led an anti-government march to Islamabad. The gunshots hit Khan's vehicle, but his spokeswoman said he was not hurt. A stone-throwing mob also attacked Khan's convoy.
Khan and Qadri have vowed their supporters will camp out in Islamabad until Sharif agrees to step down and new elections are held. Khan alleges last year's election that brought Sharif's political party to power were marred by "massive rigging."
Some 25,000 security forces are guarding the capital's streets. Internet and mobile services have been suspended in many areas.
Qadri is demanding justice after a police crackdown on an anti-government rally in June in which about a dozen people died. He said authorities are targeting his supporters using anti-terrorism laws.
Khan denies the election-rigging charges.
Earlier this week, Sharif called for a discussion of the issues, rather than political action. He has warned against what he calls "any effort to create anarchy and play with the constitution," adding the government "will not allow anyone to paralyze the state machinery or incite bloody riots."