Iceland's prime minister has resigned over secret investments revealed in the Panama Papers

Iceland's Prime Minister, Sigmundur David Gunnlaugsson, has reportedly resigned over revelations contained in the Panama Papers that he and his wife hid millions of dollars worth of investments in an offshore shell company.

Gunnlaugsson said on Tuesday that he would dissolve parliament and call a new election if he did not receive the backing of his coalition party to remain in office, Reuters reported. Thousands took to the streets on Monday to call for Gunnlaugsson's ouster.

Reports that the prime minister had resigned over the revelations first emerged late Sunday night, when giant leak of documents from the internal database of a global law firm based in Panama, called Mossack Fonseca, revealed the offshore holdings of 140 politicians, public officials, and athletes around the world.

The leaked data has not been released to the public, but it shows that Gunnlaugsson and his wife, Anna Sigurlaug Palsdottir, bought the offshore company, Wintris, in 2007 to invest millions from the sale of Palsdottir's family business, according to The Guardian. Gunnlaugsson failed to declare his 50% stake in the company and sold his share to his wife for $1 eight months later.

Gunnlaugsson walked out of an interview with the Swedish television company SVT in March when asked about his and his wife's relationship to Wintris.

The leaks - a collaborative effort by the International Consortium of Investigative Journalists - were obtained by the German newspaper Süddeutsche Zeitung and contain over 11 million records dating back 40 years.

They amount to about 3 terabytes of data, including corporate records, financial filings, and emails. It is roughly 1,500 times as big as the 1.7 gigabytes of data dumped in 2010 by Wikileaks.

While anonymous company structures hidden in offshore holdings are not illegal, the leaks reveal the extent to which many high-level political figures have relied on shell companies to conceal their wealth, launder money, or evade taxes.

A memorandum from a Mossack Fonseca partner contained in the leak reads, "Ninety-five per cent of our work coincidentally consists in selling vehicles to avoid taxes," according to The Guardian.

To that end, offshore companies can be also be used for more nefarious purposes, such as to do business with blacklisted firms or individuals.

Among those implicated are Argentine President Mauricio Macri - who was listed as a director of a Bahamas company that dissolved in 2009 known as Fleg Trading Ltd, which did business in Brazil - and the king of Saudi Arabia, who evidently used shell companies in the British Virgin islands to take out $34 million worth of mortgages for properties in London, Fusion found in a review of the documents.