Several residential buildings were damaged as a result of a Tuesday morning drone attack on Moscow, the city’s mayor said, in the latest sign that the war in Ukraine may be spreading beyond that country’s borders.

“In the early hours of this morning, a UAV attack caused minor damage to several buildings,” Mayor Sergey Sobyanin said, according to RIA Novosti, using a common acronym for drones. He added there were no casualties.

Videos shared across Russian social media showed air defenses shooting at drones in various parts of Moscow and the Moscow region. Two residential houses in different parts of Moscow were hit by drones, RIA reported earlier on Tuesday, citing an unidentified emergency service official.

“This morning, residents of some districts of the Moscow region could hear the sounds of explosions — it was our air defense system working. Several drones were shot down as they approached Moscow,” Moscow Region Governor Andrey Vorobiev said in his Telegram channel.

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While Russian regions have faced intensified attacks this month, the drone attack Tuesday morning may be the most intense against Moscow since Russia invaded Ukraine in February last year. Two drones also exploded over the Kremlin on May 3, an attack that Moscow blamed on Ukraine, which denied involvement.