Spanish protests after PM Rajoy denies slush fund claim
Protests broke out in Spanish cities after Prime Minister Mariano Rajoy denied claims that he and other party members had accepted secret payments.
"I have never received nor distributed undeclared money," Mr Rajoy said earlier, vowing not to resign.
An online petition demanding the leader's resignation has gathered more than 740,000 signatures.
El Pais newspaper had published images of ledgers showing payments to members of the governing Popular Party (PP).
The paper said Mr Rajoy had collected 25,200 euros (£22,000; $34,000) a year between 1997 and 2008.
The prime minister and his party were elected by a landslide in November 2011 on a promise to reduce the high public deficit.
'Shame of Spain'
Demonstrators took to the streets in Madrid, Barcelona, Seville and other cities on Saturday evening, calling on Mr Rajoy to step down.
Carrying banners reading "The shame of Spain" and "You will pay for corruption with prison", protesters were also demanding that the PP explain its finances.
The Associated Press reports that riot police in Madrid clashed with demonstrators.
More than 740,000 people have signed an online petition calling for the "immediate resignation" of Mr Rajoy and all PP members involved in the scandal.
Earlier, Mr Rajoy denied the media allegations in an extraordinary session with the PP national executive.
"It is not true that we received cash that we hid from tax officials," he said in a televised speech.
He added he would publish on the party's website full details of his income and assets.
As Mr Rajoy spoke, several hundred demonstrators gathered outside the party headquarters shouting "thieves" and "resign".
El Pais said the photographs it had published were of ledgers kept by former treasurers Luis Barcenas and Alvaro Lapuerta between 1990 and 2009.
Money was allegedly paid by firms via Mr Barcenas, who stepped down in 2009 and is currently under investigation for money-laundering.
Investigators recently revealed that Mr Barcenas held a Swiss bank account which at one point held as much as 22m (£19m; $30m) euros.
Until 2007, Spanish political parties were allowed to receive anonymous donations.
Spaniards have been asked to accept painful austerity measures as the government battles to avoid an international bailout. Meanwhile, the unemployment rate has reached a record 26%.
The allegations raise ethical questions about the Popular Party's dealings during the period of Spain's building boom, when politicians granted large numbers of development contracts.
The party has denied making any "systematic payment to certain people of money other than their monthly wages".