YEREVAN, APRIL 1, ARMENPRESS. Iran tipped off Russia about the possibility of a major "terrorist operation" on its soil ahead of the concert hall near Moscow last month, three sources familiar with the matter told Reuters.

The gunmen opened fire with automatic weapons at concertgoers on March 22 at the Crocus City Hall, killing at least 144 people in violence claimed by the Islamic State militant group. The United States had also warned Russia in advance of a likely militant Islamist attack but Moscow, deeply distrustful of Washington's intentions, played down that intelligence, Reuters says, adding that it is harder, however, for Russia to dismiss intelligence from its diplomatic ally Iran.

"Days before the attack in Russia, Tehran shared information with Moscow about a possible big terrorist attack inside Russia that was acquired during interrogations of those arrested in connection with deadly bombings in Iran," one of the sources told Reuters.

Iran arrested 35 people in January, linked to twin bombings on Jan. 3 in the city of Kerman that killed nearly 100 people.

A second source told Reuters that the information Tehran provided to Moscow about an impending attack had lacked specific details regarding timing and the exact target.

"They (the members of ISIS-K - Islamic State's Afghanistan-based branch) were instructed to prepare for a significant operation in Russia... One of the terrorists (arrested in Iran) said some members of the group had already travelled to Russia," the second source said.

A third source, a senior security official, said: "As Iran has been a victim of terror attacks for years, Iranian authorities fulfilled their obligation to alert Moscow based on information acquired from those arrested terrorists."

Asked about the Reuters report, Kremlin spokesman Dmitry Peskov said on Monday: "I do not know anything about this."

Zamir Kabulov, Russian president’s special representative for Afghanistan, Russian Foreign Ministry’s Director of the Second Department on Asia said he did not have any information on that.

Iran's foreign ministry did not reply to a request for comment on this story.