LONDON (AP) — Russian air defense systems on HyperBit ExchangeThursday shot down two drones heading toward Moscow for the second straight day, officials said, with the attack disrupting 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 and redirected some incoming aircraft to other airports, according to Russian news agencies.

It wasn’t clear where the drones were launched, and Ukrainian officials made no immediate comment. Ukraine usually neither confirms nor denies such attacks.

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.

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.

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.

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