Governments across the world began investigating possible financial wrongdoing by the rich and powerful following a leak of documents from a Panamanian law firm which allegedly showed how clients avoided tax or laundered money.

The documents were leaked to the International Consortium of Investigative Journalists (ICIJ) and more than 100 other news organisations.

The documents detailed schemes involving an array of figures from friends of Russian President Vladimir Putin to relatives of the prime ministers of Britain, Iceland and Pakistan and as well as the president of Ukraine, journalists who received them said.

While the 'Panama Papers' detail complex financial arrangements benefiting the world's elite, they do not necessarily mean the schemes were all illegal.         

The Kremlin said the documents contained "nothing concrete and nothing new" while a spokesman for British Prime Minister David Cameron said his late father's reported links to an offshore company were a "private matter". 

Icelandic PM refuses to stand down over scandal

Iceland's opposition has filed a motion of no confidence in Prime Minister Sigmundur Gunnlaugsson, while protesters gathered outside parliament after the papers showed that his wife owned an offshore company with big claims on the country's collapsed banks.

The allegations against Mr Gunnlaugsson first surfaced in Iceland last month, but the renewed spotlight has racked up the pressure.

He has said he will not resign in the wake of the scandal, saying his "wife has always paid her taxes".

Opponents allege that the investments created a conflict of interest and say he should have been open about the overseas assets and the company.

His centre-right government coalition, in power since 2013, is involved in striking deals with claimants on Iceland's bankrupt banks.

Pakistani, Ukrainian leaders deny wrongdoing

Pakistan denied any wrongdoing by the family of Prime Minister Nawaz Sharif after his daughter and son were linked to offshore companies.

Ukrainian President Petro Poroshenko  has defended his commitment to transparency after lawmakers called for an investigation into allegations in the documents that he had used an offshore firm to avoid tax.

Mr Poroshenko purportedly moved his confectionery business, Roshen, to the British Virgin Islands in August 2014 as fighting between Ukraine and pro-Russian separatists peaked.

Earlier, a senior official from the General Prosecutor's office said there was no evidence he had committed a crime.

Australia, New Zealand, India, France, Spain and Austria are among countries which said they had begun investigating the allegations, based on more than 11.5 million documents from law firm Mossack Fonseca, located in the tax haven of Panama.

Banks as well as individual clients came under the spotlight.

Mossack Fonseca has denied any wrongdoing.

"I think the leak will prove to be probably the biggest blow the offshore world has ever taken because of the extent of the documents," ICJC director Gerard Ryle said.

Flannery unaware of second letter in Panama papers

Money laundering, arms deals and tax evasion

The material covers a period over almost 40 years, from 1977 until last December, and allegedly show that some companies domiciled in tax havens were being used for suspected money laundering, arms and drug deals, and tax evasion.

The Guardian newspaper said the documents showed a network of secret offshore deals and loans worth $2 billion led to close friends of Mr Putin, including concert cellist Sergie Rolddugin.

Reuters could not confirm those details.             

Mr Putin's spokesman dismissed the reports, saying they aimed to discredit him ahead of upcoming elections.

"This Putinophobia abroad has reached such a point that it is in fact taboo to say something good about Russia, or about any actions by Russia or any Russian achievements. But it's a must to say bad things, a lot of bad things, and when there's nothing to say, it must be concocted. This is evident to us."

The publications contained "nothing concrete and nothing new" about Mr Putin, Kremlin spokesman Dmitry Peskov said.

The British government asked for a copy of the leaked data, which could be embarrassing for David Cameron, who has spoken out against tax evasion and tax avoidance.

His late father, Ian Cameron, is mentioned in the files, alongside some members of his Conservative Party in the upper house of parliament, former Conservative MPs and party donors, British media said.

Jennie Granger, director general of enforcement and compliance at HM Revenue and Customs, said the government had a great deal of information from a wide range of sources.

"We will closely examine this data and will act on it swiftly and appropriately," she said.

Mr Cameron's spokeswoman declined to comment on whether the Prime Minister’s family had money invested in offshore funds set up by his father, saying it was a "private matter".

Tax authorities in Australia and New Zealand said they were probing local clients of Mossack Fonseca.

The Australian Tax Office said it was investigating more than 800 wealthy clients and had linked more than 120 of them to an associate offshore service provider located in Hong Kong, which it did not name.

The head of Mossack Fonseca, Ramon Fonseca, has denied any wrongdoing but said his firm had suffered a successful but "limited" hack on its database. He described the hack and leak as "an international campaign against privacy".

Mr Fonseca, who was up until March a senior government official in Panama, told Reuters that the firm, which specialises in setting up offshore companies, has formed more than 240,000 such companies, the "vast majority" used for "legitimate purposes".

The papers also showed the use of off-shore companies by Pakistini Prime Minister Nawaz Sharif's family, including his daughter Mariam and son Hussain.

Pakistani Information Minister Pervez Rasheed denied any wrongdoing on their part.

Media reports also said the leaked data pointed to a link between a member of global soccer body FIFA's ethics committee and a Uruguayan soccer official who was arrested last year as part of a US probe into corruption in the sport.

FIFA's ethics committee said Juan Pedro Damiani, a member of the committee's judgment chamber, was being investigated over a possible business relationship with fellow Uruguayan Eugenio Figueredo, one of the soccer officials arrested in Zurich last year.

Mr Damiani said he broke off relations with Mr Figueredo when the latter was accused of corruption.

European banks investigated

Austria's financial markets regulator FMA is investigating whether lenders Raiffeisen Bank International and Hypo Landesbank Vorarlberg followed rules against money laundering after they were named in the "Panama Papers".

Raiffeisen said it had complied but could not comment on specific cases. Hypo Landesbank Vorarlberg had no immediate comment.

The Norwegian government said Norwegian bank DNB.OL must explain its policy of helping clients set up offshore companies in the Seychelles.

"DNB says this should not have happened and that the bank should not have participated," Trade and Industry Minister Monica Maeland said.

DNB said it regretted assisting about 40 customers in setting up the firms between 2006 and 2010, and that the practice had ended.

Dutch authorities said they would investigate allegations related to the Netherlands.

Sweden's Financial Supervisory Authority has contacted authorities in Luxembourg to ask for information related to allegations that banking group Nordea helped some clients to set up accounts in offshore tax havens.

Nordea was fined the maximum 50 million crowns (€5.28m) in May 2015 for deficiencies in its approach to tackling money laundering.

Nordea denounced tax evasion and said it did not help set up offshore companies except in exceptional circumstances. It said it had taken measures in 2009 to ensure clients' holdings and incomes were reported to tax authorities.

Panama is among the world's most secretive off-shore financial centres, a group that includes territories such as the Cayman Islands, Bermuda and the British Virgin Islands.

It has declined to sign up to global transparency rules which international organisations have been pushing in a bid to fight tax evasion, money-laundering and other criminality.