ISLAMABAD — Pakistan's Supreme Court banned the country's most popular opposition leader and his brother from contesting elections, igniting fresh political turmoil Wednesday as the nation battles rising al-Qaida and Taliban violence.
The long-awaited decisions against former Prime Minister Nawaz Sharif and his brother, Shahbaz, triggered anti-government demonstrations in several cities and a 5 percent drop in the main stock market on fears of street violence and protracted tensions among the country's ruling elite.
The court was hearing appeals against a ruling barring Sharif from contesting elections because of a criminal conviction dating back to his overthrow in a coup by former dictator Gen. Pervez Musharraf in 1999. It was also considering allegations of irregularities in brother Shahbaz's election to the provincial parliament
It gave no details on the rulings.
Sharif and his supporters accused President Asif Ali Zardari, the husband of slain former premier Benazir Bhutto, of exerting pressure on the court to issue the ruling to neutralize a political threat. Zardari did not immediately respond to the allegations.
"The nation should rise against this unconstitutional decision and this nefarious act of Zardari," Sharif, who heads the country's largest opposition party, said in a televised media conference. Sharif said he opposed rioting, but added: "If the people want to show their anger, who can stop them?"
Sharif urged people to join him in what was expected to be a large anti-government rally next month by lawyers whose protests in 2008 helped drive Musharraf from power after years of U.S.-backed military rule and usher in a democratically elected coalition under Zardari.
The prospect of Sharif and his supporters leading a campaign against Zardari will concern Washington, which had been hoping the political turmoil that marked Musharraf's final years was over, leaving Pakistan's rulers able to concentrate squarely on the threat posed by al-Qaida and the Taliban.
The decision prevents Sharif from challenging Zardari in general elections in 2013 and _ of more immediate importance to the opposition _ meant Shahbaz cannot continue as head of the provincial government in the country's political heartland and most populous and wealthy region, Punjab.
"The Sharifs have been effectively thrown out of politics, and they are going to react," said Shafqat Mahmood, a prominent political commentator. While the federal government was not in imminent danger, he predicted "in the next three to six months, the entire political order will become very shaky."
As a measure of Sharif's importance and influence, visiting U.S. and other Western officials frequently travel his mansion in Punjab to talk with him, the most recent being Richard Holbrooke, the American envoy to Pakistan and Afghanistan.
U.S. officials fear Pakistan's lawless border regions are being used by Islamist militants to plan attacks in neighboring Afghanistan _ and perhaps in the West.
The country of 180 million people is also up against a punishing economic crisis and is trying to soothe tensions with fellow nuclear-armed nation India over last year's terror attacks on Mumbai, which were allegedly carried out by Pakistani militants.
Sharif had cooperated with Zardari to oust Musharraf, but their alliance quickly broke down once Zardari took office amid disagreements about whether to reinstate judges fired by Musharraf. Sharif went into opposition and their relationship had grown increasingly strained.
Despite being in opposition, Sharif has so far not loudly criticized Zardari's close alliance with Washington or military offensives against the militants, despite both being unpopular among many Pakistanis.
Suspected U.S. missile strikes near the Afghan border has infuriated many Pakistanis, but are believed to have killed high-level extremists. Pakistan's Foreign Minister Shah Mahmood Qureshi said Wednesday that the U.S. should provide unmanned drone planes to allow Islamabad to instead control the missile strikes.
The Supreme Court's decision left Punjab in temporary control of the governor, a Zardari appointee. It was unclear when a new provincial government would be formed.
In the 1990s, Sharif used Punjab as a political base from which to undermine Bhutto's two terms in office. Analysts say Zardari could now form a new provincial coalition to shut the Sharifs out and leave all four Pakistan provinces under his control.
Nawaz Sharif returned from exile in 2008 seeking to contest elections, but was disqualified by a court because of a prior criminal conviction on terrorism and hijacking charges stemming from the 1999 coup.
Associated Press reporters Steve Graham and Zarar Khan contributed to this report from Islamabad.