ISLAMABAD -- Pakistan Prime Minister Nawaz Sharif is facing growing political pressure, including calls to resign, over revelations in the Panama Papers about his family's interests in assets held by offshore companies.

Leaked documents from the Panamanian law firm Mossack Fonseca showed that three of Sharif's children controlled offshore companies which owned luxury residential property in London. According to the International Consortium of Investigative Journalists website, Sharif's children Mariam, Hasan and Hussain "were owners or had the right to authorize transactions for several companies." They raised a 7 million pound ($10 million) loan from Deutsche Bank against four apartments in London's Park Lane owned by offshore companies.

Sharif, 66, is an affluent businessman with companies dealing primarily in steel but opposition figures have claimed that his wealth was partly the result of corruption, a suggestion the prime minister has always vigorously denied. His son Hussain said earlier this month that the family had done "nothing wrong."

Opposition parties, primarily Pakistan Tehreek-e-Insaf (PTI) headed by former cricketer Imran Khan, are keeping up the pressure. Khan has spent the past week in London, vowing to hire financial investigation agencies to probe the Sharif family's offshore accounts.

There are legitimate uses for offshore companies, although these entities can be used to hide the ownership of assets or to evade tax. In Sharif's case, no wrongdoing has been proven; however the prime minister is no stranger to allegations of corruption, which contributed to a premature end to his first term in the 1990s.

As the political turmoil over the Panama Papers escalated, Sharif traveled to London last week, on what he described as a planned visit for medical treatment.

The timing of his trip prompted speculation about an extended absence but doctors declared the premier fit and he returned home on Tuesday night.

"I feel much better now and with your prayers I hope it [my health] will remain well. I am going back to my country right now where I will once again start working for the revival of its economy," Nawaz Sharif told media outside his London residence before taking the plane back to Islamabad.

Opposition leader Khan is keeping up the pressure. "He is caught," he told Britain's Guardian newspaper, speaking about Sharif. "He is in trouble. I think he is going to find it impossible to govern Pakistan."

Political analysts are more cautious. "The main political parties do not want to create a space for the...military to overcome the democratic set-up," Senate chairman Raza Rabbani told the Nikkei Asian Review.

http://asia.nikkei.com/Politics-Economy/Policy-Politics/Panama-Papers-unsettle-Pakistan-s-politics