ROME (Reuters) - An American tourist convicted over the the murder of a police officer in Rome was put under house arrest on Monday by a judge in the Italian capital, judicial sources said, meaning he will be moved out of prison.

Gabriel Christian Natale-Hjorth and his friend Finnegan Lee Elder were originally given life sentences for the 2019 murder of Mario Cerciello Rega, 35, who was stabbed to death following a botched drug deal.

Both saw their initial sentences repeatedly trimmed as the case bounced around courts in the Italian multi-tiered trial system, and earlier this month an appeals court ruled that Natale-Hjorth should serve an 11-year, 4-month term.

Natale-Hjorth did not handle the knife during the attack but was tussling with another Carabinieri police officer as Elder was stabbing Cerciello Rega, according to court documents.

Elder eventually got a 15-year, 2-month term and remains in prison.

The judicial sources said judges granted Natale-Hjorth the house arrest on the request of his lawyers, and he would remain under detention at his grandmother's house in a town near Rome. There were no immediate details on the reasons for the decision.

Cerciello Rega's widow was "totally shocked by the news" of the house arrest, her lawyer Massimo Ferrandino said in a statement, and would not give further comments.

The two Americans, both from California, had tried to buy drugs during a holiday in Rome. They have said they were cheated and grabbed a bag belonging to an intermediary of the dealer as he tried to escape, the court documents said.

They later agreed on a meeting with the dealer to swap the bag for the money but two policemen showed up in plain clothes instead of him, the documents said. Italian media reported that the dealer was a police informer.

Elder and Natale-Hjorth's lawyers had argued that the two acted in self defence because they thought the two policemen were thugs who were out to get them.

Prosecutors, who had called for tougher sentencing for the two tourists, will be able to appeal the latest verdict before Italy's highest court.

(Reporting by Marco Carta; writing by Angelo Amante)