Kyiv, Ukraine - The Russian army hit Ukraine's capital Kyiv with ballistic missiles on Monday, injuring four people and damaging an uninhabited three-story building, according to officials.

Kyiv mayor Vitali Klitschko said two of the four injured were in a central neighborhood and taken to hospital. Rocket debris also fell in two other areas.

According to the Ukrainian air force, two ballistic missiles were fired at the city of millions from the Russian-controlled Crimea peninsula. Both were shot down.

Half a dozen explosions from anti-aircraft missiles had previously been heard in the city center. The air raid warning was only triggered a few seconds beforehand, it said.

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The Defense Ministry said Monday that the country's air defense has shot down 2,000 Russian cruise missiles or rockets since Moscow launched its all-out attack on February 24, 2022.

"That's a result of the titanic work of Ukrainian air defenders. Thousands of lives were saved by modern air defense systems provided by our partners," the ministry wrote in a post published on X, formerly Twitter.

However, the ministry did not specify how many rockets and cruise missiles managed to get past Ukraine's air defense system. It also didn't list the number of intercepted combat drones, which have played a major role in the war.

The ministry echoed President Volodymyr Zelensky's repeated request for additional air defense systems from Ukraine's Western allies, with the US in particular having significantly slowed down its deliveries.

"Ukraine still needs more air defense systems to protect our people from Russian terror. Because civilian infrastructure remains the primary target of Russian strikes."

Russian aerial drones struck the Ukrainian electricity grid in the Odessa and Mykolaiv regions in the south of the country in the early hours of Monday, the Ukrainian military reported.

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Power cuts occurred in parts of Odessa and its hinterland. The city authorities said they were forced to halt tram and trolleybus services. No injuries were reported.

A substation in the Mykolaiv region caught fire after taking a hit, the state-owned Ukrenergo energy supply company reported.

The military authorities reported that debris from a drone hit a two-story residential building in the region, setting it alight and injuring 11 people, two of them seriously.

Russian forces have increasingly targeted Ukrainian energy infrastructure over recent days.