Russias top investigative body announced Monday that it will look into alleged involvement by the United States, Ukraine and other Western countries in terrorist attacks inside Russia.Top Russian officials, including President Vladimir Putin, have suggested that Ukraine and the West were partly responsible for the Crocus City Hall attack last month, but they have yet to bring forward any concrete evidence to back up the claim.The Islamic States affiliate ISIS-K has said it was responsible for the massacre, the deadliest in Russia since the 2004 Beslan school siege, and social media channels linked to the militant group published graphic videos of the gunmen killing people at the music venue outside Moscow.Kyiv and the West have denied any involvement and accused Russian officials of exploiting the tragedy.Russias Investigative Committee, which probes major crimes, said in a video statement released on Monday that it will look into the organization, financing and conduct of terrorist acts by the United States, Ukraine and other Western countries directed against Russia.The investigation will scrutinize the provided information and make a procedural decision as part of the inspection, it said.The Investigative Committee said the move was in response to requests by several Russian lawmakers and public figures, including the nationalist political philosopher Alexander Dugin.Meanwhile, Reutersreported Monday that Russian ally Iran had warned Moscow about the possibility of a major terrorist operation days ahead of the Crocus City Hall attack.Like the United States own previous warning of an attack in Russia, Tehrans warning lacked specific details about ISIS-Ks target and timeframe of the attack, Reuters said, citing three anonymous sources familiar with the issue.Russias Foreign Ministry later said it was unaware of Irans warnings about the attack, whileKremlin spokesman Dmitry Peskov told Reuters: I do not know anything about this.