ROME (Reuters) - The son of Iran's deposed shah has appealed to Italian Prime Minister Matteo Renzi to intervene to help an Iranian activist jailed in Italy, saying he risks execution if he is extradited.

Reza Pahlavi, whose late father was toppled by the 1979 Islamic Revolution in Iran, wrote to Renzi on Monday, two days after Mehdi Khosravi was arrested in a hotel in Lecco, near Lake Como in Italy's Alpine north.

Lecco police said in a statement they had carried out an international arrest warrant issued by the Iranian government which aimed to have the 37-year-old extradited "for the crime of corruption".

Pahlavi posted the letter, written from his Paris office and addressed to Renzi personally, on a Twitter account where he describes himself as an "advocate of secularism and parliamentary democracy in Iran".

"Any attempt to force Mr Khosravi's return to Iran will lead to his incarceration, torture and possible conviction and execution as a political and human rights opposer of the regime," the letter said.

Pahlavi said Khosravi had been living in Britain as a political refugee since fleeing the Islamic Republic shortly after "the 2009 demonstrations and uprising" surrounding disputed elections.

"This critical humanitarian matter requires your indispensable intervention so that Mr. Khosravi can return to the United Kingdom."

A spokesman for Renzi directed a request for comment to Italy's foreign ministry, which declined to comment.

Iran's application of the death penalty, which has drawn repeated criticism from human rights organizations, leapt last year, according to the United Nations, which counted nearly 1,000 executions.

Khosravi felt unwell after his arrest and was taken to hospital before being transferred to prison, the Lecco police statement said.

A judge responsible for preliminary investigations has yet to formalize Khosravi's detention, the Italian newspaper Corriere della Sera reported on Tuesday.

(Reporting by Isla Binnie; editing by Mark Heinrich)