Pakistani anti-corruption officials are to appear before the Supreme Court on Thursday over orders to arrest the prime minister and 15 other people on accusations of graft in 2010.
The country's top judge ordered that all those accused of graft in power generation projects be arrested and for the chairman of the anti-corruption National Accountability Bureau (NAB) to report to the court.
Coming as a populist cleric leads tens of thousands of protesters outside parliament to demand that the government resign, Tuesday's order sparked panic about an alleged judiciary-military plot to derail elections due by mid-May.
Interior Minister Rehman Malik threatened overnight to disperse the crowd unless leader Tahir-ul Qadri ends the demonstration, the largest political rally in the capital for years, but President Asif Ali Zardari later intervened to stop authorities from using force against protesters.
The rally has threatened to destabilise the nuclear-armed country as it inches towards what would be the first democratic transition of power between two civilian governments at the upcoming elections.
The economy is struggling, Taliban and other violence is at a high, the rupee is sinking, there is an appalling energy crisis and fledgling peace gains with India appear in jeopardy following five deadly cross-border shootings in a week.
"The NAB chairman is going to appear before the Supreme Court tomorrow," NAB lawyer Aamir Abbas told AFP late on Wednesday.
Asked if any arrests were made so far, as ordered by the court, Abbas replied: "I am not aware about arrests."
Commentators doubt that Prime Minister Raja Pervez Ashraf will be detained imminently given that the case has already been running for years.
Lawyers say that even if he is arrested for questioning over the allegations, which date back to his time as water and power minister, he can remain in office unless and until he is convicted.
An estimated 25,000 people are believed to be taking part in the largest rally in the capital since the current government took office in 2008.
On Wednesday, the main opposition parties demanded an immediate timetable for elections, but refused to join Qadri, threatening to isolate him as his rally moves into a fifth day on Thursday.
"An election schedule and caretaker set-up should be announced without any delay and dates for these events specified forthwith," said opposition leader Nawaz Sharif, who was unseated as prime minister by a military coup in 1999.
The government has announced no date for polls but says parliament will disband in mid-March to make way for a caretaker government and elections within 60 days.
Qadri wants parliament dissolved now and a caretaker government set up in consultation with the military and judiciary to implement key reforms such as setting up a new election commission and banning corrupt candidates.
"People should refrain from making any demands which are not in the ambit of the constitution," hit back Sharif.
Qadri's sudden - and apparently well-financed - emergence after years in Canada has been criticised as a ploy by the establishment, particularly the armed forces, to delay the elections and sow political chaos.
Information minister Qamar Zaman Kaira has ridiculed the cleric, accusing him of staying in a "seven-star bunker" while women and children camp out in the chilly nights and issued a veiled threat alluding to his possible arrest.
While critics dismiss Qadri's supporters as a rent-a-crowd, many of Qadri's supporters articulate real concerns about Pakistan's problems, digging in for the long-haul, with supplies of food, water and mattresses and blankets.
Police clashed briefly with stone throwers and protesters on Tuesday, shooting into the air and firing tear gas. Eight officers were injured.
Rally organisers accused police of opening fire and trying to arrest Qadri.
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