The purpose of Prime Minister Binyamin Netanyahu's visit to Moscow in September was to hand the Kremlin a list of Russian scientists who, Israel believes, are helping Iran to develop a nuclear warhead, the British Sunday Times newspaper reported.
"We have heard that Netanyahu came with a list and concrete evidence showing that Russians are helping the Iranians to develop a bomb," the paper quoted a source close to the Russian defense minister as saying last week.
"That is why it was kept secret. The point is not to embarrass Moscow, rather to spur it into action," the anonymous source reportedly explained.
During the short and tense meeting, Netanyahu named the Russian experts said to be assisting Iran in its nuclear program, the paper quoted Israeli sources as saying.
The Jerusalem Post could not independently confirm the report.
In September, a senior Kremlin official confirmed to the Russian paper Kommersant that Netanyahu made a clandestine trip to Russia, and said that "this kind of development could only be related to new and threatening information on Iran's nuclear program."
The Russian newspaper quoted experts speculating that such a trip would only be justified under extraordinary circumstances, "for example, in the case of Israel planning to attack Iran."
The report came despite a statement from the Kremlin press service that "nothing is known" about reports of the visit. Dmitry Peskov, a spokesman for Russian Prime Minister Vladimir Putin, also said he had no information, the Interfax news agency reported.
Nevertheless, there was never any official denial of the report from Moscow.
At the time, the Prime Minister's Office appeared to stick to its original version of events: that Netanyahu was occupied with "secret and classified activities" during his unexplained absence of over 12 hours.
Herb Keinon contributed to this report.