KYIV, Ukraine — Russian air defense systems on Thursday shot down two drones heading toward Moscow for a second straight day, officials said. The reported attack disrupted flights at two international airports as Ukraine appeared to step up its assault on Russian soil.

One drone was downed in the Kaluga region southwest of Moscow and another near a major Moscow ring road, according to Moscow Mayor Sergey Sobyanin and the Russian Defense Ministry, which blamed the attack on Ukraine.

No casualties or damage were immediately reported.

Domodedovo airport, south of the city, halted flights for more than two hours and Vnukovo airport, southwest of the city, stopped flights for more than two and a half hours, according to Russian news agencies. Ten flights were diverted, Russia’s Federal Agency for Air Transport said.

Firing drones at Moscow after more than 17 months of war has little apparent military value for Ukraine, but the strategy has served to unsettle Russians and bring home to them the conflict’s consequences.

Kyiv officials, as usual, neither confirmed nor denied Ukraine’s possible involvement in the drone strikes, though Air Force spokesman Yurii Ihnat remarked: “This cannot but please us because people in Moscow thought they were safe. Now, the war affects each and every Russian.”

“We now see that ‘something’ happens in Moscow on a regular basis,” he added.

Russia’s Defense Ministry also said it had stopped Ukrainian drone attacks in Moscow-annexed Crimea. It said it shot down two drones near the port city of Sevastopol and electronically jammed nine that crashed into the Black Sea.

On Wednesday, Ukrainian media reported social media blogs as saying that a thick plume of smoke billowed over Sevastopol, which is the headquarters of Russia’s Black Sea Fleet.

The governor of Sevastopol, Mikhail Razvozhayev, said the smoke came from a “fleet training exercise” and urged local residents not to worry.

The incidents have come against the backdrop of Ukraine’s ongoing counteroffensive, which Ukrainian and Western officials have warned will be a long slog against the Kremlin’s deeply entrenched forces.

US to Send Additional $200 Million in Supplies

The Pentagon is to provide Ukraine with another $200 million in weapons and ammunition to help sustain the counteroffensive, according to U.S. officials.

Ukraine has already received more than $43 billion from the U.S. since Russia invaded last year.

Ukraine’s presidential office said at least six civilians were killed and 27 were injured between Wednesday and Thursday mornings.

In eastern Ukraine’s Donetsk province, Russia shelled 16 cities and villages, and three people were killed, the office reported. In Zaporizhzhia, three people were killed and nine wounded, including an 11-month-old baby.

Meanwhile, 12 people remained missing after an explosion Wednesday at a factory that makes optical equipment for Russian security forces, Russia’n state news agency RIA Novosti reported, citing emergency officials.

Russia’s Emergency Ministry said 71 people required medical assistance after the explosion.

Russian officials did not offer a suspected cause of the explosion at the Zagorsk plant in the region around Moscow, which added to jitters about potential Ukrainian drone strikes.

The fallout from Russia’s war against Ukraine has brought concerns to neighboring countries, including the presence of Russia-linked Wagner group mercenaries in Belarus this summer after their short-lived mutiny in Russia.

Poland’s defense minister said Thursday that the country intends to put 10,000 soldiers along its border with Belarus amid fears of a spike in illegal immigration.

Polish officials have accused Belarusian authorities of organizing illegal border crossings to disrupt and pressure Warsaw, which along with other NATO countries has provided support for Kyiv’s war effort.