ISLAMABAD (AFP) - The chairman of Pakistan's financial regulator was arrested on Friday (July 21), accused of forging documents in a corruption case against Prime Minister Nawaz Sharif that has gripped the country.

Head of the Securities and Exchange Commission Zafar Hijazi was accused by investigators of doctoring the records of a sugar mill owned by the Sharif family.

Mr Hijazi, who is seen as a trusted ally of Mr Sharif, had appeared in court on Friday morning for a bail hearing and was arrested during the proceedings.

The arrest comes just over a week after the investigating team, tasked by the Supreme Court with probing the graft claims, said that documents naming Mr Sharif's daughter Maryam as a trustee for several of the family's high-end London properties were also "falsified".

Dated 2006, they were typed in Microsoft's Calibri font, which was not released for commercial use until 2007, the joint investigation team (JIT) said, citing forensics experts.

The allegations are fuelling intense pressure on Mr Sharif from opposition parties to resign. His main political rival, cricketer-turned-opposition leader Imran Khan, has called for him to be sent to prison.

"The Prime Minister's final destination is Adiala jail. Now I am not demanding his resignation, but imprisonment," he told reporters on Thursday.

But Mr Sharif has been defiant, insisting he has no reason to step down.

"This is not accountability. This is exploitation," Mr Sharif said while addressing supporters in the northern region of Dir on Thursday.

The controversy erupted last year with the publication of 11.5 million secret documents from Panamanian law firm Mossack Fonseca documenting the offshore dealings of many of the world's rich and powerful.

Three of Mr Sharif's four children - Maryam, his presumptive political heir, and his sons Hasan and Hussein - were implicated in the papers.

In April, the Supreme Court said there was insufficient evidence to oust Mr Sharif from power, but ordered the formation of the JIT to probe the claims.

Its report, issued earlier this month, included the Calibri claims and concluded that there was a "significant disparity" between the Sharif family's income and lifestyle.

The report was submitted to the Supreme Court, which on Friday said it had come to a decision on the case - though there was no immediate indication what its verdict will be or when it will be announced.

The Sharif family has consistently denied the allegations against it and rejected the JIT report, dismissed by the ruling PML-N party as "trash".

Pakistan is due to hold a general election next year.