Kyiv has cultivated sabotage cells inside Russia and has started supplying them with Ukrainian-made drones, CNNreported Monday, citing multiple unnamed sources familiar with United States intelligence.The noticeable increase in drone attacks on Russian soil starting with an early May strike on the Kremlin is likely a culmination of months of work, one of the sources was quoted as saying.The cells are believed to be a mix of well-trained Ukrainian operatives and pro-Ukraine sympathizers.Kyiv reportedly supplies its cell with drones via the vast and very difficult to control Russian-Ukrainian border.As a result, CNN reported that United States officials believe the May 3 attack on the Kremlin was launched from within Russia.Despite public criticism, United States and Western officials privately laud Ukraines cross-border attacks as a smart military strategy that could divert Russian resources to protecting its own territory.Kyiv itself has not acknowledged any role in the attacks.A United States source who had spoken to Ukrainian officials in recent days said Kyiv plans to continue the attacks as a good distraction tactic for Russian troops, according to CNN.The stepped-up drone strikes come ahead of a widely anticipated Ukrainian counteroffensive aimed at retaking lands occupied by Moscow.Independent Russian media says the number of acts of sabotage inside the country hasmore than doubled so far in 2023.Russias domestic intelligence agency, the Federal Security Service (FSB), has announced several arrests of Ukrainian or pro-Ukrainian saboteurs in recent weeks.This spring, the head of the FSB accused Kyiv and the West of recruiting young Russians to stage armed attacks in their home country.Russian law enforcement authorities have stepped up random car inspections and announced a series of restrictions on drone flying after the embarrassing incidents that exposed gaps in Russias domestic security.