Peru's appeals court overturned opposition leader Keiko Fujimori's arrest for money laundering and ordered "her immediate release" on Wednesday.

After a four-hour session, the court found in favour of Fujimori, who earlier had argued that preventative arrests can only occur when there is a danger of the accused fleeing or obstructing the work of the judiciary, adding that neither of those risks existed in her case.

"This party is not a criminal organization. I ask you to take a fair decision," Fujimori told the court.

Judge Octavio Sahuanay, in charge of the appeals session, said that there were irregularities in the defendant's detention and agreed that it had no legal basis as she was not at risk of fleeing.

The 43-year-old leader of right-wing Popular Force (FP), the biggest party in parliament, has been detained since October 10 on charges of money-laundering.

Several of Fujimori's aides have also been arrested on charges of laundering illicit funds that entrepreneurs allegedly contributed to her 2011 presidential campaign.

Fujimori's arrest came a week after the Supreme Court overturned a pardon that had been granted to her father, former president Alberto Fujimori, who is now due to serve the 15 years that remain from his 25-year prison sentence for human rights abuses. He is currently under arrest at a Lima medical clinic.