ISLAMABAD — Pakistani opposition leader Imran Khan suspended talks with the government Thursday after it appointed a new police chief in the capital ahead of a possible crackdown on thousands of antigovernment protesters who have besieged Parliament.
Khan, a famed cricketer-turned-politician, and fiery cleric Tahir-ul-Qadri have led massive protests from the eastern city of Lahore to the gates of Parliament in Islamabad to demand the resignation of Prime Minister Nawaz Sharif, accusing him of rigging the vote that brought him to power last year.
The protests have raised fears of unrest in the nuclear-armed US ally with a history of political turmoil, and after a request from the country’s powerful military, the government convened talks with Khan and Qadri’s representatives early Thursday.
Shah Mahmood Qureshi, a senior leader of Khan’s party, told reporters that the opposition presented six demands, including Sharif’s resignation.
The other demands include electoral reforms, setting up a caretaker government, removing top election officials, and accountability for anyone found to have rigged last year’s elections, which marked the first democratic transfer of power in Pakistan after a long history of coups and dictatorships.
It is unlikely Sharif would give ground on those demands, which the government considers illegal.
Later Thursday, Khan told supporters that the government had removed the Islamabad police chief for not using force against him, and warned that the new police chief, Khalid Khattak, would follow orders to disperse the protests, which have thus far been peaceful.
‘‘I have suspended the talks with the government,’’ Khan said. He warned that his supporters would storm the prime minister’s office if officials staged any crackdown. It was not immediately clear if Qadri was also pulling out of the talks.
The government denied it had any plans to confront the protesters.
‘‘We want to carry forward the talks to solve this issue,’’ Information Minister Pervaiz Rashid said.
Another Cabinet minister, Ahsan Iqbal, said government negotiators held initial talks with Khan’s Tehrik-e-Insaf party — the legislature’s third largest — before dawn Thursday. ‘‘We again went to an agreed place today for more talks, but the team of Imran Khan did not turn up,’’ he said.
He added that the government wanted to find a ‘‘win-win solution.’’
Tensions spiked Wednesday when Qadri asked his supporters to block the main gates of the Parliament building and prevent lawmakers from going in or out.
He also asked supporters to prevent Sharif from walking from Parliament to his nearby office, but the prime minister later used a back exit.
On Thursday, Sharif was back in Parliament, where lawmakers adopted a resolution rejecting the opposition’s ‘‘unconstitutional demands’’ and vowing to ‘‘uphold the supremacy of the constitution’’ and the ‘‘sovereignty of the Parliament.’’
Sharif was forced from office after a previous stint as prime minister in 1999, when the then-army chief Pervez Musharraf seized power in a coup.
Sharif’s decision this week to give the military responsibility for handling the protests may be perceived as a sign of weakness, longtime US defense intelligence analyst John McCreary wrote in his NightWatch newsletter, published by KGS Government Solutions, Inc.