Russia's Defense Ministry said the incident took place in the early hours of Monday, and three servicemen were killed by debris at the Engels airbase that houses the Tu-95 and Tu-160 nuclear-capable strategic bombers that have been involved in launching strikes on Ukraine.

Engels is located in Russia's Saratov region on the Volga river, more than 600 kilometers (more than 370 miles) east of the border with Ukraine.

No damage was inflicted on Russian aircraft, the ministry said.

It is the second time Engels has been targeted by Ukrainian drones; on Dec. 5, unprecedented drone strikes on Engels and the Dyagilevo base in the Ryazan region in western Russia killed a total of three servicemen and wounded four more. The strikes on the airbases were followed by a massive retaliatory missile barrage in Ukraine that struck homes and buildings and killed civilians.

In Ukraine, the night from Sunday into Monday appeared unusually quiet. For the first time in weeks, the Russian forces didn't shell the Dnipropetrovsk region, which borders the partially occupied southern regions of Kherson and Zaporizhzhia, its Gov. Valentyn Reznichenko reported on Telegram.

``This is the third quiet night in 5.5 months since the Russians started shelling`` the areas around the city of Nikopol, Reznichenko wrote. Nikopol is located across the Dnieper River from the Zaporizhzhia nuclear power plant, which is under control of the Russian forces.

Ukrainian-controlled areas of the neighbouring Kherson region were shelled 33 times over the past 24 hours, according to Kherson's Ukrainian Gov. Yaroslav Yanushevich. There were no casualties.

On Saturday, a deadly attack on the city of Kherson, which was retaken by Kyiv's forces last month, killed and wounded scores.