Ukraine’s capital came under another ballistic missile attack early Wednesday, injuring at least 53 people on the ground, including six children, and damaging buildings, officials said. A series of loud explosions could be heard in Kyiv at 3 a.m. local time as the city's air defenses were activated for the second time this week. Ukraine’s air force said Russia launched 10 ballistic missiles toward the capital and all were intercepted by air defenses. The attack on the capital underscored the continuing threat to Ukraine from the Kremlin’s missile arsenal in the 21-month war. Russia has in recent months been stockpiling its air-launched cruise missiles from its heavy bomber fleet, according to a recent assessment by the U.K. Ministry of Defense. That may herald another heavy winter bombardment of Ukraine’s power grid. Moscow last year targeted energy infrastructure in an effort to deny Ukrainians heat, light and running water and break their fighting spirit. Ukraine has dwindling supplies of air defense munitions and other ammunition. The shortage has prompted Ukrainian President Volodymyr Zelenskyy to visit Washington on Tuesday in an effort to persuade lawmakers to approve President Joe Biden's request for $61.4 billion for Ukraine. Zelenskyy on Wednesday arrived in Norway to meet Nordic leaders gathered for a regional meeting focusing on cooperation in security and defense issues. Senior leaders from Denmark, Iceland, Norway, Finland and Sweden — among Kyiv's staunchest supporters — attended. Debris from intercepted missiles fell in Kyiv's eastern Dniprovskyi district, injuring at least 53 people, Kyiv Mayor Vitali Klitschko said on Telegram. Twenty people, including two children, were hospitalized, and 33 people received medical treatment on the spot. An apartment building, a private house and several cars caught fire, while the windows of a children's hospital were shattered, Klitschko said. Falling rocket debris also damaged the water supply system in the district. It wasn't immediately clear what type of missile was used in the Kyiv attack.