Russian authorities say three Ukrainian drones attacked Moscow in the early hours on Sunday, injuring one person and prompting a temporary closure for traffic of one of four airports around the Russian capital.

It was the fourth such attempt at a strike on the capital region this month and the third this week, fueling concerns about Moscow’s vulnerability to attacks as Russia's war in Ukraine drags into its 18th month.

The Russian Defense Ministry referred to the incident as an “attempted terrorist attack by the Kyiv regime" and said three drones targeted the city. One was shot down in the surrounding Moscow region by air defense systems and two others were jammed. Those two crashed into the Moscow City business district in the capital.

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Photos from the site of the crash showed the facade of a skyscraper damaged on one floor. Moscow Mayor Sergei Sobyanin said the attack “insignificantly damaged” the outsides of two buildings in the Moscow City district. A security guard was injured, Russia's state news agency Tass reported, citing emergency officials.

No flights went into or out of the Vnukovo airport on the southern outskirts of the city for about an hour, according to Tass, and the air space over Moscow and the outlying regions was temporarily closed for any aircraft. Those restrictions have since been lifted.

Moscow authorities have also closed a street for traffic near the site of the crash in the Moscow City area.

There was no immediate comment from Ukrainian officials, who rarely if ever take responsibility for attacks on Russian soil.

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Russia's Defense Ministry reported shooting down a Ukrainian drone outside Moscow on Friday. Two more drones struck the Russian capital on Monday, one of them falling in the center of the city near the Defense Ministry’s headquarters along the Moscow River about 3 kilometers (2 miles) from the Kremlin. The other drone hit an office building in southern Moscow, gutting several upper floors.

In another attack on July 4, the Russian military said four drones were downed by air defenses on the outskirts of Moscow and a fifth was jammed by electronic warfare means and forced down.

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