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Pakistani Prime Minister Yousuf Raza Gilani (center) is escorted by security as he waves upon his arrival at the Supreme Court building in Islamabad on April 26.

Pakistan's Prime Minister Yusuf Raza Gilani was disqualified by the country's top court and declared ineligible to hold office Tuesday.

On April 26, judges convicted Gilani in contempt of court proceedings for refusing to open a corruption probe against President Asif Ali Zardari. The court said Tuesday that Gilani should not have held office since that verdict was announced.

The April ruling was previously questioned by the speaker of the National Assembly, who decided that the court order did not cast any doubt on the premier's right to hold office.

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But the speaker's decision was struck down Tuesday by a bench of judges headed by the Chief Justice of Pakistan, Iftikhar Chaudhry.

After his contempt of court conviction in April, Prime Minister Gilani had 30 days within which he could file an appeal. He failed to do so, arguing that the President enjoyed immunity from prosecution -- but his failure to file an appeal rendered the earlier conviction final, and disqualifed him from office.

Gilani had the opportunity to challenge the conviction legally, but chose instead to stand on principle. 

"Since no appeal was filed (against the April 26 conviction) ... therefore Syed Yusuf Raza Gilani stands disqualifed as a member of the Majlis-e-Shoora (parliament)," Chaudhry said in a packed courtroom, according to Reuters.

"He has also ceased to be the prime minister of Pakistan ... the office of the prime minister stands vacant," the judge added.

Gilani's lawyer, Fawad Chaudhry, told The Associated Press that only parliament could dismiss the prime minister. 

The Supreme Court ruling came in response to petitions filed against Gilani for not standing down after the conviction. 

Emergency meetings
In their written order Tuesday, judges reminded Zardari that he is "required to take necessary steps under the Constitution to ensure continuation of the democratic process."

Senior leaders of Gilani's party -- the PPP (Pakistan People's Party) -- were reportedly in emergency meetings Tuesday. The party does enjoy a majority in parliament to elect their chosen successor.

The civilian government has been lurching from crisis to crisis for the majority of the last year, in what many saw as a power struggle between the powerful army, judiciary, and government.

Tuesday's action is likely to throw the government into further turmoil, as they struggle to become the first civilian government to complete a full five-year term before the scheduled elections in February 2013. The instability could lead to early elections being called. 

A U.S. official, speaking on condition of anonymity, said Pakistani leaders are so consumed with keeping their government stable and remaining in power, they're unable to devote the necessary attention nor make any bold decisions to re-engage with the U.S. and get the alliance back on track.

The overland NATO supply lines which run through Pakistan have been closed since November, shuttered in protest about a U.S. cross-border strike in which 24 Pakistani soldiers were killed.

A U.S. team recently spent weeks in Pakistan, negotiating new rates to re-open those supply lines, but left without any resolution. 

Reuters and The Associated Press contributed to this report.

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Pakistan's Prime Minister Yusuf Raza Gilani waves to supporters upon arrival at the Supreme Court for a hearing in a contempt-of-court of notice, in Islamabad, Thursday.

ISLAMABAD -- Pakistan's Supreme Court on Thursday found Prime Minister Yusuf Raza Gilani guilty of contempt of court for refusing to reopen corruption cases against the president, but gave him only a symbolic sentence of a few minutes' detention in the courtroom.

Gilani smiled when the verdict was read out in a packed courthouse. He had refused to abide by a court order to write a letter to Swiss authorities to reopen a $60-million money-laundering case against President Asif Ali Zardari.

It was unclear if the token sentence would defuse political uncertainty in Pakistan, where the president and prime minister have jousted with the military and judiciary. Despite the light sentence, Gilani could still face dismissal from office in the weeks, or more likely, months to come.

"For reasons to be recorded later, the prime minister is found guilty of contempt for wilfully flouting the direction of the Supreme Court," said Justice Nasir-ul-Mulk.

The conviction means Gilani is the first serving prime minister in Pakistan's history to be convicted by a court, but his detention lasted just a few minutes until the session was adjourned. He could have faced up to six months in jail and the loss of office.

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"I think what they've done is taken it from the legal arena and chucked it into the political arena," said Cyril Almeida, a prominent columnist for the Dawn daily newspaper.

He said opposition members of parliament now might move to expel Gilani from office.

"There will be massive pressure from the opposition, the media, from civil society, saying 'He's been convicted for flouting the letter of the law and he should go home,'" Almeida said. "There will be a lot of pressure for him to resign."

Tight security
A throng of supporters surrounded Gilani as he walked into the court in Islamabad, showering him with rose petals. Security was tight, with about 1,000 police officers standing by in riot gear and helicopters circling the Supreme Court building.

Gilani's lawyers had said before the verdict that he would not automatically be disqualified from office if convicted, and at any rate he would be able to appeal against the verdict.

"This is a historic day. The court has declared a lawmaker a lawbreaker. This is weakening democracy in Pakistan," said Firdous Ashiq Awan, former information minister.

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The case stems from what many observers say is a political battle between the government and the military, which has held the whip hand in Pakistan's political arena for most of the country's 64 years of independence. Many say the army is using the court to keep the government on the back foot.

The source of the current conflict is a graft case against Zardari that involves kickbacks he and his late wife, former Prime Minister Benazir Bhutto, allegedly received from Swiss companies when Bhutto was in power in the 1990s. They were found guilty in absentia in a Swiss court in 2003.

Zardari appealed, but Swiss prosecutors ended up dropping the case in 2008 after the Pakistani government approved an ordinance giving the president and others immunity from old corruption cases that many agreed were politically motivated.

The Pakistani Supreme Court ruled the ordinance unconstitutional in 2009 and ordered the government to write a letter to Swiss authorities requesting they reopen the case against Zardari. Gilani has refused, saying the Pakistani constitution grants the president immunity from criminal prosecution while in office.

NBC News' Fakhar ur Rehman, Reuters and The Associated Press contributed to this report.