The government has said it "welcomes" the information revealed by an international group of journalists and that upon PM Modi's orders, a team with experts on tax, foreign exchange transactions will work with financial crime-fighting agencies to investigate "the flow of information in each one of the cases."

However, not all offshore dealings are illegal. Companies or trusts can be set up in low tax places like Panama for legitimate uses such as business finance, mergers and acquisitions and estate or tax planning.

That is not always the case. The highly secretive laws of Panama make it easy to conceal the real ownership of companies set up there. In many cases reported on in The Panama Papers, there are details of how some of the world's most powerful people used offshore havens to conceal their fortunes and dodge taxes. Often, this is done through shell companies, initially incorporated without significant assets or operations, to disguise information about the funds involved.

The offshore accounts are based on documents from a law firm named Mossack Fonseca, which is in Panama. It has described the release of information as "an international campaign against privacy".

More than 100 media groups - including The Indian Express- collaborated in the investigation and combed through millions of emails, financial records and passport details.

The Indian Express says its eight-month investigation of over 36,000 files has revealed around 500 Indian names linked to the Panama law firm whose records were hacked. The newspaper lists some of the country's biggest film stars and billionaires.

It was only in 2013 that Indians were permitted to set up companies abroad. Some of the people and corporates named by the Express allegedly routed money to these offshore ventures much before that. Others -like actor Aishwarya Rai Bachchan -have denounced the report as "totally untrue".

The government is under significant pressure to reveal and recover black or untaxed money, a promise stressed by the PM in his election campaign. The Supreme Court is monitoring the findings of a Special Investigating Team or SIT of experts.

A dozen current or former heads of state are named in the Panama Papers, including Chinese President Xi Jinping, Pakistan Prime Minister Nawaz Sharif and the king of Saudi Arabia.