Defeated Iranian presidential candidate Akbar Hashemi Rafsanjani has reacted angrily to his surprise loss to hardline opponent Mahmoud Ahmadinejad.
Rafsanjani was the favourite going into the election
In his first public statement following the election result, the moderate cleric alleged that an illegal dirty tricks campaign had been mounted.
The US meanwhile said Iran was out of step with current trends in the region.
Mr Ahmadinejad won 62% of the vote in Friday's presidential run-off poll - nearly twice Mr Rafsanjani's backing.
The conservative president-elect said his win was a blow to the country's enemies - an apparent reference to the US, which had criticised the election as flawed.
Mr Rafsanjani, who was president between 1989 and 1997, was the favourite going into the election and had re-cast himself as a liberal who was more willing to engage with the West.
Conservatives are now in control of every elected and unelected institution of government in Iran.
In a statement carried by the ISNA news agency, Mr Rafsanjani said: "All the means of the regime were used in an organised and illegal way to intervene in the election."
He condemned "those who spent hundreds of billions of rials (tens of millions of US dollars) of the people's money to defame me and my family".
However, Mr Rafsanjani said he would not be appealing against the result, saying Iran's judiciary had shown it "cannot or do not want to do anything. This I will leave to God."
The 70-year-old concluded: "I entered this election uniquely to serve the revolution, Islam, Iran and the people. Those who weakened a competitor chose to weaken the revolution.
"I hope the country will be cleared of these enemies and profiteers who are without logic or faith."
Mr Rafsanjani nonetheless said that "everyone should help" President-elect Ahmadinejad, who is currently the Mayor of Tehran.
The White House responded to the poll result by expressing support for "those who call for greater freedom for the Iranian people".
The State Department said Iran was "out of step... with the currents of freedom and liberty that have been so apparent in Iraq, Afghanistan and Lebanon".
UK Foreign Secretary Jack Straw said there were "serious deficiencies" in the election, noting that many reformists, and all women candidates, had been barred from standing.
He urged the new president to deal with international concerns over Iran's nuclear programme.
The European Union said it was ready to work with "any Iranian government" willing to progress on the questions of human rights, nuclear energy and other matters of concern.
'Humiliation for US'
In his first public statement following the result, Mr Ahmadinejad said he wanted to "build up an exemplary, developed and powerful Islamic society".
On the economy, Mr Ahmadinejad said he would favour Iranian companies when awarding oil contracts, and talked of removing what he called ambiguities and a lack of transparency.
Mahmoud Ahmadinejad appealed to Iran's poor
The BBC's Frances Harrison in Tehran says it is not yet clear whether this is just more of the populist rhetoric which brought Mr Ahmadinejad to power, or an indication that he is planning a major economic shake-up in the world's second largest oil producer.
Iran's supreme leader, Ayatollah Ali Khamenei, described Mr Ahmadinejad's victory as a "profound humiliation" for the US.
Mr Ahmadinejad, 49, who campaigned on a conservative Islamic platform, had surprised observers by beating five other candidates in the first round to reach the run-off.
Some 22 million people voted in Friday's run-off poll - a turnout of 60%, down from 63% in the first round a week ago.
Interior ministry officials monitoring polling stations received some 300 complaints of electoral violations in Tehran alone, the Associated Press news agency reports.
The Guardians Council, which ran the poll, has dismissed allegations of election fraud.
Mr Ahmadinejad will be Iran's first non-cleric president for 24 years when he takes office in August.