Russian air defence systems have shot down two drones heading towards Moscow for the second straight day, officials said.
The 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 south-west of Moscow and another near a major Moscow ring road, according to Moscow mayor Sergey Sobyanin and the Russian defence 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, south-west 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 was not 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 defence 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 counter-offensive, 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 counter-offensive, according to US officials.
Ukraine has already received more than $43 billion from the US 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 on Wednesday at a factory that makes optical equipment for Russian security forces, Russia’s 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 neighbouring countries, including the presence of Russia-linked Wagner group mercenaries in Belarus this summer after their short-lived mutiny in Russia.
Poland’s defence minister said 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 organising illegal border crossings to disrupt and pressure Warsaw, which along with other Nato countries has provided support for Kyiv’s war effort.
