Russian air defenses on Tuesday foiled a Ukrainian drone attack on Moscow that prompted authorities to briefly close one of the city’s international airports, officials said, as a Western analysis said that Russia has managed to slow Kyiv’s recently launched counteroffensive.

The drone attack, which follows previous similar raids on the Russian capital, was the first known assault on the city since an abortive mutiny launched 11 days ago by mercenary chief Yevgeny Prigozhin. His Wagner troops marched on Moscow in the biggest — though short-lived — challenge to Russian President Vladimir Putin in more than two decades of his rule.

Authorities in Ukraine, which generally avoids commenting on attacks on Russian soil, didn’t say whether it launched the drone raid.

The Russian Defense Ministry said that four of the five drones were downed by air defenses on the outskirts of Moscow and the fifth was jammed by electronic warfare means and forced down.

There were no casualties or damage, Moscow Mayor Sergei Sobyanin said.

As with previous drone attacks on Moscow, it was impossible to verify the Russian military’s announcement that it downed all of them.

The drone attack prompted authorities to temporarily restrict flights at Moscow’s Vnukovo airport and divert flights to two other Moscow main airports. Vnukovo is about nine miles southwest of Moscow.

In May, two daring drone attacks jolted the Russian capital, in what appeared to be Kyiv’s deepest strikes into Russia.

Tuesday’s raid came as Ukrainian forces have continued probing Russian defenses in the south and the east of their country in the initial stages of a counteroffensive.

Oleksiy Danilov, the secretary of Ukraine’s Security and Defense Council, said that the military was currently focusing on destroying Russian equipment and personnel, and that the past few days of fighting have been particularly “fruitful.” He provided no evidence and it wasn’t possible to independently verify it.

The Ukrainians are up against minefields, anti-tank ditches and other obstacles, as well as layered defensive lines reportedly up to 12 miles deep in some places as they attempt to dislodge Russian occupiers.

Ukrainian Deputy Defense Minister Hanna Maliar said Tuesday evening that Russia was increasing the intensity of its shelling on Ukraine’s northern border in order to keep Ukrainian forces there.

The U.K. Defense Ministry said Tuesday the Kremlin’s forces have “refined (their) tactics aimed at slowing Ukrainian armored counteroffensive operations in southern Ukraine.”

Moscow has placed emphasis on using anti-tank mines to slow the onslaught, the assessment said, leaving the attackers at the mercy of Russian drones, helicopters and artillery.

“Although Russia has achieved some success with this approach in the early stages of Ukraine’s counteroffensive, its forces continue to suffer from key weaknesses, especially overstretched units and a shortage of artillery munitions,” the assessment said.

Western analysts say the counteroffensive, even if it prospers, won’t end the war, which started with Russia’s full-scale invasion in February 2022.

Russia, meanwhile, has continued its missile and drone barrage deep behind the front line.

Russian shelling of Pervomaiskyi, a city in Ukraine’s northeastern Kharkiv region, wounded 43 civilians, Kharkiv Gov. Oleh Syniehubov said Tuesday. Among the wounded were 12 children, including two babies, according to officials.

Oleksandr Lysenko, mayor of the city of Sumy in northeastern Ukraine, said that three people were killed and 21 others were wounded in a Russian drone strike on Monday that damaged two apartment buildings.

Ukrainian President Volodymyr Zelenskyy said the attack also damaged the regional headquarters of the Security Service of Ukraine, the country’s main intelligence agency. He argued that the country needs more air defense systems to help fend off Russian raids.

In all, Ukraine’s presidential office reported Tuesday, at least seven Ukrainian civilians were killed and 35 others injured in the fighting over the previous 24 hours.

Ukrainian military officials additionally warned Tuesday that Russian forces might be preparing to stage a provocation at the Russian-occupied Zaporizhzhia nuclear power plant.