Ukrainian President Volodymyr Zelenskyy acknowledged for the first time that his country’s military forces were fighting in a surprise military incursion into Russia’s Kursk border region.

In his night video address, Zelenskyy said he discussed the ongoing incursion “to push the war onto the aggressor’s territory” with top Ukrainian commander Oleksandr Syrskyi.

“Ukraine is proving that it can indeed restore justice and ensure the necessary pressure on the aggressor,” he said.

Meanwhile, Ukraine’s incursion into Russia continued for a sixth day. The largest such attack since the full-scale invasion and unprecedented for its use of Ukrainian military units on Russian soil, it caught Moscow unaware and was an embarrassment to Russian military leaders who have scrambled to contain the breach.

The exact aims of the operation remain unclear and Ukrainian military officials have adopted a policy of secrecy, presumably to ensure its success. Military experts have said that it is likely intended to draw Russian reserves away from the intense fighting in Ukraine’s eastern Donetsk region, while a presidential advisor suggested it may strengthen Kyiv’s hand in any future negotiations with Russia.

Overnight, fighting continued between the two countries as a Russian drone and missile barrage on Kyiv killed two people including a 4-year-old boy. The bodies of a 35-year-old man and his son were found under rubble after fragments of missiles fell on a residential area in Kyiv’s suburban Brovary district, according to Ukraine’s State Emergency Service on Sunday. Another three people in the district were also injured in the attack.

In Russia, Kursk’s regional governor said that a Ukrainian missile shot down by Russian air defenses fell on a residential building, wounding 13 people.

Russia attacked Ukraine with four ballistic missiles and 57 Shahed drones, Ukraine’s Air Force said. Air defenses shot down 53 drones.

Zelenskyy, citing preliminary information, said that Russia had used a North Korean missile in the strike. Ukraine and the U.S. have previously said that Russia has used North Korean missiles in the war.

Zelenskyy reiterated calls to Western allies to step up in assistance to Ukraine, and that “to really stop Russian terror, we need not only a full-fledged air shield that will protect all our cities and communities, but also strong decisions from partners — decisions that will remove restrictions on our defensive actions.”

In Russia, the Defense Ministry said 35 drones were shot down overnight over the Kursk, Voronezh, Belgorod, Bryansk and Oryol regions.

Ukraine has not commented on the Sunday drone attacks inside Russia. But it comes as Ukraine has increased the pace of similar drone attacks largely targeting military infrastructure and oil depots in recent weeks.

Meanwhile, Belarus said it was sending more troops to its border with Ukraine on Saturday, saying Ukrainian drones had violated its airspace as part of Kyiv’s military incursion into Russia’s Kursk region.

Authoritarian leader Alexander Lukashenko said Belarusian air defense forces destroyed dozens of targets flying from Ukraine over the Mogilev region, which borders Russia, on Friday evening.

“The Ukrainian armed forces violated all rules of conduct and violated the airspace of the Republic of Belarus. In the eastern direction, very close to us in the Kostyukovichi district,” Lukashenko said at a meeting in Minsk on Saturday.

Belarusian Defense Minister Viktor Khrenin said Belarus regards the violation of its airspace as a provocation and is “ready for retaliatory action.”