Iran alerted Russia to security threat before Moscow attack, sources say

Iran tipped off Russia about the possibility of a major "terrorist operation" on its soil ahead of the concert hall massacre near Moscow last month, Reuters reports quoting three sources familiar with the matter.

In the deadliest attack inside Russia in 20 years, 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.

It is harder, however, for Russia to dismiss intelligence from diplomatic ally Iran on the attack, which has also raised questions over the effectiveness of Russian security services. Moscow and Tehran, both under Western sanctions, have deepened military and other cooperation during the two-year Ukraine war.

"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, including a commander of Islamic State's Afghanistan-based branch ISIS-Khorasan (ISIS-K), who it said were linked to twin bombings on Jan. 3 in the city of Kerman that killed nearly 100 people.

Islamic State claimed responsibility for the Iran blasts, the bloodiest since the 1979 Islamic Revolution. US intelligence sources said ISIS-K had carried out both the Jan. 3 attacks in Iran and the March 22 shootings in Moscow.

Islamic State once occupied large swathes of Iraq and Syria, imposing a reign of terror and inspiring lone-wolf attacks in Western countries, but was declared territorially defeated in 2017.

However, ISIS-K, one of its most fearsome branches, has raised the group's profile again with large-scale bloodshed.

ISIS-K, named after an old term for a region that encompassed parts of Iran, Turkmenistan and Afghanistan, emerged in eastern Afghanistan in late 2014 and quickly established a reputation for extreme brutality.

A second source, who also requested anonymity due to the sensitivity of the issue, said 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) 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 April 1: "I do not know anything about this."

Iran's foreign ministry did not reply to a request for comment on this story. The White House had no comment on the matter.

A source familiar with the US intelligence on an impending attack in Russia said it was based on interceptions of "chatter" among ISIS-K militants.

Challenging the US assertions, Russia has said it believes Ukraine was linked to the attack, without providing evidence. Kyiv has strongly denied the assertion.