"The war in Iraq was a disaster, the occupation of Iraq is a disaster," Zapatero, 43, told Cadena Ser radio.

He spoke just before the European Union held three minutes' silence in tribute to the 200 people killed in last Thursday's bombings of crowded Madrid commuter trains.

An ongoing investigation into the attacks has found growing evidence they were carried out by Islamic extremists linked to al-Qaeda as punishment for Spain's help in the invasion and occupation of Iraq.

Voters turned out in force for Sunday's elections. Many of them expressed anger at retiring Prime Minister Jose Maria Aznar when he cast his ballot, jostling and booing him while some shouted "Aznar: your war, our dead."

Zapatero, whose Socialist Party ended eight years of rule by Aznar's Popular Party (PP) after winning 43 percent of the ballots to the PP's 38 percent, said near-total public opposition to the Iraq war had been key.

He said that barring new developments in Iraq before June 30 -- the date the United States has promised to hand power over to an Iraqi provisional government -- Spain's 1,300 troops in Iraq "will return home" as he had promised before the elections.

The other occupying states will be contacted for consultations on withdrawing the soldiers, he said.

Zapatero also said Bush and his main ally, British Prime Minister Tony Blair, need to engage in "self-criticism".

"You can't bomb a people just in case" they pose a perceived threat, Zapatero said in statements just five days before the first anniversary of the March 20 start of the war.

"You can't organise a war on the basis of lies," he said, alluding to Bush's and Blair's insistence the war was justified by their belief -- so far unfounded -- that Iraq had weapons of mass destruction that posed an imminent threat.

"Wars such as that which has occurred in Iraq only allow hatred, violence and terror to proliferate," he said.

The head of the EU executive arm, European Commission chief Romano Prodi, agreed in an interview published by Italy's La Stampa newspaper Monday.

"It is clear that using force is not the answer to resolving the conflict with terrorists," Prodi said. "Terrorism is infinitely more powerful than a year ago," and all of Europe now feels threatened, he told the paper.

The loss of the United States' and Britain's main ally has left Bush especially looking exposed as he faces the November presidential election.

While Zapatero fielded congratulations from French President Jacques Chirac, South African President Thabo Mbeki and other world leaders, Bush had yet to make a call.

Other US allies in Iraq, among them Poland and Denmark, were notably cool towards his win.

Polish foreign ministry spokesman Boguslaw Majewski said: "Our general position is that everybody there (in Iraq) should stay until the situation is stabilised."

Spain's contingent is the sixth-largest in Iraq. It has suffered 11 deaths, including seven intelligence agents ambushed in November.