Russia unleashed a barrage of missiles and drones across Ukraine early Thursday, killing at least 13 people and wounding dozens more.

Ukrainian President Volodymyr Zelenskyy said the hours-long attack struck Kyiv and the surrounding region as well as Odesa and Chernihiv, damaging apartment buildings, a children’s hospital and a school in the capital. Twelve people were killed in Kyiv and another in the surrounding region, he said, with around 40 injured.

“Unfortunately, while Moscow is investing in ballistic missiles and escalation, such strikes do not always receive the response they should from the world,” Zelenskyy wrote on X. “As long as Ukraine does not have enough anti-ballistic defense, Russia will not consider peace seriously.” U.S.-made Patriot interceptors “cannot yet be replaced,” he added.

Russia’s defense ministry said it used air-, land- and sea-launched weapons to strike military facilities and warehouses. Moscow also claimed its forces had shot down 726 Ukrainian drones.

Kyiv Mayor Vitali Klitschko declared Aug. 21 a day of mourning “in memory of the victims of the enemy’s massive attack on the capital.” Flags will be lowered and entertainment events banned as emergency crews continue working across three districts of Kyiv.

The barrage also put neighboring NATO countries on alert.

Romania’s defense ministry announced that a drone “entered Romanian national airspace” at 3:21 a.m. before crashing minutes later near Grindu “in an uninhabited area.” No casualties or damage were reported.

Poland meanwhile scrambled military aircraft as Russian strikes continued in neighboring Ukraine. The Polish military said it had activated available forces and assets, while ground-based air-defense and radar systems were put “in a state of readiness.”