A son of Pakistani Prime Minister Nawaz Sharif has defended his family's ownership of offshore companies, saying the family has done "nothing wrong".
Leaked documents show that three of Mr Sharif's children were linked to offshore companies that owned properties in London, local media say.
Some opposition leaders have called for Mr Sharif to be investigated over his family's "wealth stashed abroad".
However, Mr Sharif's son Hussain said all their business affairs were legal.
The allegations stem from a leak of 11 million documents held by the Panama-based company Mossack Fonseca to German newspaper Sueddeutsche Zeitung, which were then shared with the International Consortium of Investigative Journalists (ICIJ).
There are legitimate ways of using tax havens and offshore companies, although these entities are often used to hide the true owners of assets or avoid paying tax on the money.
Maryam, Hasan and Hussain Nawaz Sharif were either owners of, or had the right to authorise transactions for, the offshore companies, the ICIJ said.
The records indicated the family owned London real estate in prime locations and that the companies used the properties as collateral to secure a loan worth millions of pounds, the report said.
Umar Cheema from the Center for Investigative Reporting in Pakistan told AFP: "Nawaz Sharif does not own any company but having companies in the name of his children also raises questions."
Meanwhile, Imran Khan, chairman of the opposition Tehreek-e-Insaf party, said: "If the NAB [National Accountability Bureau] wants to maintain its credibility, it should immediately begin a probe into Nawaz Sharif's family."
"Nawaz Sharif should explain how his children made all this money," he said, while questioning whether they had paid tax on their income.
However, Hussain Nawaz Sharif told Geo TV: "Those apartments are ours and those offshore companies are also ours... There is nothing wrong with it and I have never concealed them."
He was not resident in Pakistan, so he did not have to declare his assets, he said, adding: "We fully follow all rules and regulations in doing any business."
Local media say more than 200 Pakistanis have been identified in the Panama Papers, including business owners, politicians and members of the judiciary.
Meanwhile, in neighbouring India, Finance Minister Arun Jaitley said a group had been set up to monitor the exposes and crack down on illegal financial holdings abroad.
The Indian Express said about 500 Indians were listed in the Panama papers, including Bollywood stars Amitabh Bachchan and Aishwarya Rai.
Mr Bachchan was appointed director in at least four offshore shipping companies in 1993, registered in the British Virgin islands and Bahamas, the newspaper said, adding that Mr Bachchan had not responded to requests for comment.
Meanwhile, Ms Rai and her family were appointed as directors of a company incorporated in the British Virgin Islands in 2005, which was dissolved in 2008, Indian Express said.
A media adviser to Ms Rai questioned the authenticity of the leaked document and told the newspaper: "All information that you have is totally untrue and false."
Ms Rai is married to Amitabh Bachchan's son Abhishekh.
Panama Papers - tax havens of the rich and powerful exposed
- Eleven million documents held by the Panama-based law firm Mossack Fonseca have been passed to German newspaper Sueddeutsche Zeitung, which then shared them with the International Consortium of Investigative Journalists. BBC Panorama is among 107 media organisations - including UK newspaper the Guardian - in 76 countries which have been analysing the documents. The BBC doesn't know the identity of the source
- They show how the company has helped clients launder money, dodge sanctions and evade tax
- Mossack Fonseca says it has operated beyond reproach for 40 years and never been accused or charged with criminal wrong-doing
- Tricks of the trade: How assets are hidden and taxes evaded
- Panama Papers: Full coverage; follow reaction on Twitter using #PanamaPapers; in the BBC News app, follow the tag "Panama Papers"
- Watch Panorama on the BBC iPlayer (UK viewers only)