Shah Mehmood Qureshi.

Opposition leader Shah Mehmood Qureshi was detained on Saturday, his Pakistan Tehrik-e-Insaf (PTI) party said, just hours after he said it would challenge any delay to the country's election in the courts.

As per sources, the Federal Investigation Agency (FIA) took Qureshi into custody from his Islamabad residence in connection with the ongoing investigation into cipher which PTI alleges contained the threat from the United States to oust Imran Khan from power. Qureshi has been arrested in Islamabad, claimed his party on X, formerly Twitter.

“PTI vice chairman Shah Mahmood Qureshi has been illegally arrested once again,” the social media post on the party’s account said, adding that he was taken into custody by a large contingent of police from his residence in the federal capital. According to the PTI, Qureshi was being taken to the FIA's headquarters.

Party spokesman Zulfi Bukhari told Reuters the specific reason for the detention of Qureshi, twice Pakistan's foreign minister, was not immediately clear. The caretaker information minister did not immediately respond to a request for comment.

Party spokesman Zulfi Bukhari condemned the arrest on the social media platform X, formerly known as Twitter, saying he was "arrested for doing a press conference and re-affirming PTI stance against all tyranny and pre-poll rigging that is going on currently in Pakistan."

However, he later said while speaking to Reuters that the specific reason for the detention of Qureshi, twice Pakistan's foreign minister, was not immediately clear.

PTI party chairman Imran Khan is currently jailed for three years after being convicted on graft charges and is barred from contesting any election for five years. He denies any wrongdoing. The election is meant to be held within 90 days of parliament being dissolved last week, by November, but uncertainty looms over the date as the nation grapples with constitutional, political and economic crises.

The outgoing government approved a new census in its final days, meaning new electoral boundaries must be drawn up by the Election Commission.

The exercise of drawing fresh boundaries for hundreds of federal and provincial constituencies in a country of 241 million people may take six months or more, according to a former commission official.

The election commission said on Thursday that new constituencies would be finalised by Dec.14, state television reported. After that, the commission will confirm an election date.

Electoral experts have suggested that process could see the nationwide vote pushed back several months, possibly until February. "It will be unconstitutional if the 90 days deadline is breached," Qureshi, who is leading the PTI, following Imran Khan’s arrest, told the press conference. He said the party planned to contest any delay at the Supreme Court.

According to a media report, Qureshi denied reports of "differences within PTI," saying "no one can replace party chief Imran Khan.”

Addressing a press conference in Islamabad, Qureshi termed the reports of differences within PTI’s core committee ‘false’ and said a media group was trying to spread confusion among the party’s ranks, earlier during the day. "There is no truth to such reports, no one is replacing Imran Khan,” the PTI vice chairman said.

Imran will not be tried under Army Act 1952 in the cipher case, said a report quoting an unnamed source.

The source said that although certain offences under the Official Secrets Act 1923 are tried under Army Act of 1952, in the case of Khan’s offence he will be arraigned in a criminal court under normal judicial system.

The FIA has recently booked Khan under Official Secrets Act for mishandling the cipher issue but has not shared it with the media. It is being kept secret for unexplained reasons.

Presently, FIA is in the final stages of its investigations on the matter. Some senior lawyers have also been engaged to prepare the prosecution’s case for the court. The case will be filed on behalf of the FIA, the source said, adding that it may not take much time to take up the matter before the court for trial.

The source said that certain offences under the Official Secrets Act are tried under the Army Act by military authorities. However, in the case of Khan, the source assured, he will be tried in a criminal court.