panama papers
The impact of the leaked documents from a Panamanian law firm is snowballing.
The president said wealthy corporations should not be "gaming the system."
He worried that a 2011 free trade agreement would help corporations and rich people hide their money.
Prime Minister Sigmundur David Gunnlaugsson became the first major casualty of the Panama Papers revelations.
WHAT'S HAPPENING
The U.S. Department of Justice would determine whether there was evidence of corruption and other violations of U.S. law, a spokesman said.
An online petition demanding Gunnlaugsson's resignation has amassed more than 28,000 signatures.
The documents have implicated several world leaders.
"You are asking me nonsense."
The head of Mossack Fonseca said his firm had fallen victim to "an international campaign against privacy."
Leaked documents show he and his wife were creditors to three banks that failed in 2008, even as he campaigned against creditor bailouts.