Pakistani opposition leader Imran Khan on Sunday called on Prime Minister Nawaz Sharif to resign over documents leaked from a Panama-based law firm that he said indicate that the premier's sons own several offshore companies.

Addressing a news conference at his residence in Islamabad, Khan warned he would stage a rally outside Sharif's residence in the eastern city of Lahore if the prime minister does not quit. He attached no date to the ultimatum.

Information Minister Pervaiz Rashid rejected Khan's demand, saying Sharif will not quit over "baseless allegations."

Last week, Sharif announced the establishment of an independent judicial commission to probe whether his family illegally owns offshore companies and property, as indicated in the so-called Panama Papers. Khan said the Panama Papers show Sharif himself is linked to at least two companies.

Khan also alleged that Sharif and his family were involved in corruption and tax evasion.

A massive leak of more than 11 million documents from Panama-based law firm Mossack Fonseca — one of the world's largest creators of shell companies — has been dogging political leaders around the world.

Khan, a former cricket star, is the leader of Pakistan Tahrik-e-Insaf, which made a strong showing in the 2013 elections. The following year, he staged a sit-in outside parliament for weeks, demanding Sharif step down over allegations of fraud in the election. The demonstrators gradually dispersed, and the protest was formally ended after a Taliban attack on a school in the city of Peshawar in which 150 people, mostly children, were killed.