ROME — Prime Minister Giuseppe Conte of Italy said his country’s intelligence services had informed the American attorney general, William P. Barr, that they played no role in the events leading to the Russia investigation, taking the air out of an unsubstantiated theory promoted by President Trump and his allies in recent weeks.

“Our intelligence is completely unrelated to the so-called Russiagate and that has been made clear,” Mr. Conte said in a news conference in Rome on Wednesday evening after spending hours describing Italy’s discussions with Mr. Barr to the parliamentary committee on intelligence.

Mr. Conte publicly acknowledged for the first time that Mr. Barr had twice met with the leaders of Italy’s intelligence agencies after asking them to clarify their role in a 2016 meeting between a Maltese professor and a Trump campaign adviser on a small college campus in Rome, Link Campus University.

During a subsequent meeting, the professor, Joseph Mifsud, told the adviser, George Papadopolous, that Russia had obtained damaging information about Hillary Clinton in the form of “thousands of emails,” according to the special counsel’s report into Russian meddling in the 2016 American election. Mr. Papadopolous later shared that information with foreign diplomats, which eventually set off alarms among American intelligence officials about Russian interference.