Pakistan’s main opposition party has called for a judicial investigation into allegations of rigging at last week’s general elections, which handed victory to the party led by a former cricketer.

The Pakistan Muslim League-Nawaz (PML-N) — the party of jailed ex-prime minister Nawaz Sharif — lost Wednesday’s elections to rival Pakistan Tehreek-e-Insaf led by former cricket star Imran Khan.

Khawaja Asif,  a senior leader of PML-N, demanded the creation of a “judicial commission” to launch an investigation into incidents that took place on July 25, the day of the election.

“We will issue a white paper on the election rigging and other incidents,” he told reporters in Lahore.

Asif further said that his party “will not accept these elections as legitimate and we are ready to ... start movement along with other parties.”

Another senior leader of PML-N and former interior minister, Ahsan Iqbal, also said, “Pakistan witnessed the most disputed elections in the country’s history.”

During the campaign, Shahbaz Sharif, the younger brother of ousted prime minister Nawaz Sharif who heads the party, alleged that the military had influenced the judiciary to deny him a second term.

The military, which ruled the country for about half the time since the country’s formation in 1947, denied the allegations.

After two days of vote counting, the Pakistani Election Commission declared Khan’s party the winner of the elections, rejecting earlier fraud allegations.

EU observers said on Friday that the results were “credible,” but they were critical of climate in the run-up to the vote, describing it as “uneven.”

Imran Khan, who will probably become the next prime minister, has opened coalition talks with at least one smaller party and independent politicians. He will likely take the oath of office before August 14.

Sharif transferred to hospital

In the meantime, ex-premier Sharif, who was imprisoned on corruption charges earlier this month, was taken to hospital for a minor heart attack on Sunday.

According to a government official and Sharif’s party, he was hospitalized at Pakistan Institute of Medical Sciences amid tight security.

He is currently staying in the hospital’s cardiac ward which has been declared a sub-jail.

Sharif returned from London earlier this month, along with his daughter Maryam. Both, however, were taken into custody. Sharif faces 10 years in jail and his daughter will be imprisoned for seven years.