Pakistan's Supreme Court on Wednesday barred main opposition leader and former premier Nawaz Sharif from holding office and contesting elections, sparking political turmoil in the nuclear-armed nation.
The court order also applied to his brother Shahbaz Sharif, leading to the immediate collapse of his government in the central Punjab province, Pakistan's most populous state and the country's political heartland.
The government enforced governor's rule in Punjab, the regional parliament was suspended and provincial governor Salman Taseer, a member of the main ruling Pakistan People's Party, took over the powers of chief minister.
"All petitions have been dismissed by the Supreme Court," senior lawyer Akram Sheikh told reporters in the capital Islamabad.
The highest court in Pakistan upheld a court order last June disqualifying Nawaz Sharif, throwing out an appeal lodged on their behalf by the current civilian government.
The move triggered a political showdown as Sharif accused President Asif Ali Zardari of manipulating the verdict to throw him out of politics and urged the nation to rise up against the court order.
"This is not an attack on us, but an attack on Pakistan. We have to hold accountable all those people who are bent upon destroying Pakistan."
Soon after the verdict hundreds of furious protesters took to the streets, burning tyres to block traffic and condemning Zardari while the country's stock market, shed five percent amid political uncertainty.
Lawyers called for rallies and a two-day court boycott in protest.
The Sharif brothers, whose Pakistan Muslim League-N (PML-N) is the second biggest party in the country, refuse to recognise any judge appointed by former president Pervez Musharraf under emergency rule declared in November 2007.
The PML-N campaigns to reinstate judges sacked by Musharraf and Sharif accused Zardari of reneging on promises to do so.
"Now the case has come to the court of the 160 million people of Pakistan. I think the nation will have to rise against such actions," he said.
"If not, the country will be harmed by those who want to destroy Pakistan. We should save the country against potential dangers."
A court in Lahore ruled last June that Nawaz Sharif, ousted by Musharraf in a 1999 coup, was ineligible to stand in a by-election because of criminal convictions.
He was convicted of "hijacking" a Pakistani commercial airliner carrying Musharraf after denying the aircraft landing rights while he was prime minister on 12 October 1999. The plane eventually landed and Musharraf seized power.
Sharif's brother, who has been acquitted of murder charges, was disqualified on the grounds of defaulting bank loans and ridiculing the judiciary.
Shahbaz Sharif left his office as chief minister of Punjab without protocol, driving himself to the family estate in Raiwind near Lahore.
An angry mob of some 800 people gathered on the main Mall Road in Lahore, blocking traffic by burning tyres and chanting slogans against Zardari.
Witnesses said the crowd, including women supporters, attacked banners of the main ruling Pakistan People's Party and tore down hoardings carrying pictures of the president, prime minister and the provincial governor.
Similar protests were held in dozens of major cities and towns across the country.
Analysts said the nuclear-armed Muslim nation, which is battling Taliban and Al-Qaeda extremists and reeling from attacks that have killed more than 1,600 people in less than two years, could ill afford a showdown.
"The court should have considered the situation. Can the country afford political confrontation at this stage?" said political analyst Shafqat Mahmood.
"We badly need national reconciliation. This (judgement) is not good for the country and not good for this region," said veteran politician and leader of the secular Awami National Party, Asfandyar Wali.
Punjab PPP president Qasim Zia, however refused to comment.
"This is a court verdict and we cannot say anything," he said.