Russian air defense systems destroyed three drones early Tuesday on their approach to Moscow, according to the city's mayor.Moscow Mayor Sergei Sobyanin said air defense had "destroyed drones which were trying to carry out an attack" on the Russian capital, adding that there had been no casualties.Russia's Defense Ministry said one of the drones was flying over the Kaluga region, located just southwest of Moscow, when it was brought down, while a second was destroyed northwest of the capital.A third drone was destroyed in the Tver region, also northwest of Moscow.Moscow and its surrounding regions have been targeted frequently by Ukrainian drone attacks in recent weeks.Sobyanin said there had been damage in the Istrinsky district northwest of Moscow "as a result of falling debris" and noted that emergency services were responding to the scene.