London: Pakistan's Supreme Court is considering corruption allegations against Prime Minister Nawaz Sharif, amid mounting pressure over his family's wealth, reports BBC.

The move comes after investigators said his family had failed to account for the source of its financial assets.

The probe began when the Panama Papers leaks linked his children to offshore companies used to buy London flats.

This fuelled suspicion the companies were used to launder ill-gotten wealth, claims Mr Sharif strenuously denies.

He says the properties in London were acquired legitimately and that he personally does not own them.

But the issue is turning into a major challenge to him. Opposition groups accuse his family of using their political influence to amass wealth by unlawful means and are calling on him to resign. So far Mr Sharif has refused, calling the investigators' report a compilation of "allegations and assumptions". His decision to stay in power was endorsed by the federal cabinet last week.

Hundreds of security personnel have been deployed around the Supreme Court, parts of which have also been fenced with barbed wire.  The Joint Investigation Team (JIT), set up in April, says it has found "significant gaps/disparity among the known and declared sources of income and the wealth" accumulated by Mr Sharif and his family.

It accuses Mr Sharif of concealing assets, overstating the wealth of his father with the aim of justifying his family's wealth, and of not reflecting in his wealth statement an "exorbitant hike" in his family's wealth during his first decade in power (1985-93).

It accuses his heir-apparent, daughter Maryam Sharif, of being the "beneficial owner" of offshore firms through which the London flats were acquired, and of forging documents to show she was a trustee for her brother, the real owner.

This allegation is based on a copy of a trust deed which she signed in February 2006. The JIT says the document was printed in Calibri font, which was not commercially available until January 2007.

The existence of the flats and the offshore companies linked to them was disclosed in the leak of 11 million documents held by the Panama-based law firm Mossack Fonseca.