Russian hacker and alleged spam kingpin Peter Levashov, who was arrested in Spain on a US warrant, claims he previously worked for President Vladimir Putin's United Russia party, Reuters reports, citing a report by the RIA news agency.

Levashov, 36, was arrested by Spanish authorities while on holiday in Barcelona on a US warrant in April. He has been detained since his arrest with the US Justice Department seeking his extradition from Spain.

He faces multiple charges in the US related to his alleged creation and operation of the Kelihos botnet – a massive global network of tens of thousands of infected computers used to harvest login credentials, distribute bulk spam emails and infect other computers with ransomware and other malicious software. The US Justice Department has since neutralised and taken down the sprawling botnet.

US prosecutors are seeking a 52-year jail sentence for Levashov who has been described as "one of the world's most notorious criminal spammers". The Russian has denied the hacking allegations and is currently fighting his extradition to the US.

Levashov, who also went by the aliases Peter Severa and Peter of the North, told a court in Madrid on Thursday (28 September) that he worked for the United Russia party for the last 10 years.

He added that he would be tortured for information about his political work if he is extradited to the US to face the charges against him.

"If I go to the US, I will die in a year," Levashov was quoted as saying, Reuters reports. "They want to get information of a military nature and about the United Russia party. I will be tortured, within a year I will be killed, or I will kill myself."

He did not provide any specific details regarding his work for the party. However, RIA reported he claimed he was an officer in the Russian army who had access to classified information.

"I collected different information about opposition parties and delivered it to the necessary people at the necessary time," he said.

RIA reports that Russia has also requested Levashov's extradition last week.

The report comes amid ongoing congressional investigations into Russian meddling in the 2016 presidential election and alleged collusion between President Donald Trump's campaign and the Kremlin. In January, US intelligence agencies concluded that Putin ordered a multifaceted "influence campaign" to hurt Hillary Clinton's chances and boost Trump's prospects of winning the vote.

Russia has continued to dismiss the allegations as "baseless" and has denied any involvement in the cyberattacks targeting the DNC.

In April, a US Justice Department official said Levashov's arrest was a criminal matter and did not seem to have any apparent connection to US national security.