Islamabad - Police Thursday used teargas and baton-charged supporters of Pakistan's largest opposition party in a second day of protests over a court ruling that put an election ban on its leader and former prime minister Nawaz Sharif.

Violence broke out in Islamabad where angry protesters pelted police with stones and set ablaze six vehicles, including a police van, along the highway linking the capital with the rest of the country. "Several" people were injured, police said.

The crowd blocked roads with burning tyres and smashed shop windows and those of a bank in the adjoining city of Rawalpindi.

Demonstrations were also held across Punjab, the country's largest province and a stronghold of Sharif's party, where businesses remained closed.

The protests had broken out on Wednesday immediately after the Supreme Court barred the country's most popular leader, Sharif, from running for parliament.

It also nullified last year's election of his brother, Shahbaz Sharif, to the Punjab Assembly, removing him from the seat of chief minister.

One Sharif supporter was killed in Wednesday's protest as the demonstrators burned a bakery and damaged a bank building, the daily Jang reported.

The Sharif brothers allege that President Asif Ali Zardari was behind the court verdict, widening political rifts between the two traditional rivals.

These had allied briefly after the February 2008 elections to form a coalition government and successfully oust former military strongman Pervez Musharraf.

Prime Minister Yusuf Raza Gilani, who is from Zardari's Pakistan Peoples Party (PPP), said the verdict had hurt his government's efforts for a national reconciliation.

"By banning the Sharif brothers, democracy has been weakened," he told reporters in Islamabad.

Following the court ruling, Zardari imposed federal rule and stopped the regional assembly from holding a session in Punjab, where Sharif's Pakistan Muslim League-Nawaz (PML-N) is in power, apparently in a bid to block PML-N from choosing a new chief minister.

Provincial legislators from Sharif's party gathered outside the Punjab Assembly in the eastern city of Lahore on Thursday, but police did not allow them to enter the building which was also locked to prevent holding a session. Dozens of them were briefly detained.

The PML-N has called for countrywide protests against Sharif's disqualification, which was imposed because of his conviction on several charges, including plane hijacking, after then army chief Musharraf toppled his government in a military coup in 1999.

Sharif was later pardoned but exiled for more than seven years, only to return a few weeks before the February 2008 polls. His party emerged as the second largest and forged an alliance with Zardari's Pakistan People's Party to form a coalition government.

He parted ways with Zardari after refusing to reinstate the independent-minded chief justice Iftikhar Chaudhry, who was sacked by Musharraf in November 2007 in a bid to avoid disqualification for a second term in the president's office by the court.

The brewing political crisis has also set alarm bells ringing for Western governments, as they want Pakistan to focus on the fight against al-Qaeda and the Taliban who have sanctuaries on vast swathes of ungoverned land in the north-west.

However, the US government has publicly said that the electoral ban on Sharif and his brother "is an issue for Pakistan to deal with." (dpa)