Ukrainian drone attacks killed at least five people in different parts of Russia and set fire to another warehouse belonging to Russia's largest online retailer, Wildberries, Russian officials said on Sunday, as both countries continued exchanging long-range drone strikes.

Russian authorities said a Ukrainian drone hit a Wildberries warehouse in the Samara region, about 800 kilometres from the Ukrainian border, causing a fire. Regional Governor Vyacheslav Fedorishchev said there were no casualties.

Wildberries, often compared to Amazon in Russia, has come under repeated Ukrainian attacks in recent weeks. Since mid-July, Ukrainian drones have struck more than a dozen of the company's warehouses as Kyiv seeks to disrupt Russia's economy and logistics during the ongoing war.

Russia's Defence Ministry said its air defence systems shot down 635 Ukrainian drones overnight, including some over Russian-occupied Crimea and the Black and Azov seas. The ministry did not say how many drones Ukraine had launched or how many reached their targets.

Ukraine's air force, meanwhile, said Russia launched 133 drones overnight, with 24 reaching their intended targets.

In Russia's Saratov region, Governor Roman Busargin said two people were killed after a Ukrainian drone hit a residential building. The attack also damaged civilian infrastructure in the cities of Engels and Saratov.

Engels is home to a major Russian military airbase, while Saratov has one of the country's large oil refineries. Both cities have been frequent targets of Ukrainian drone attacks.

In Russia's Bashkortostan region, Governor Radiy Khabirov said air defences repelled a large-scale drone attack on industrial facilities in the city of Ufa. He said a fire broke out but did not specify which facility had been hit.

In the Udmurt Republic, acting regional head Olga Abramova said three civilians were killed and two others injured in a Ukrainian drone strike. She said Russian air defences shot down two drones but a civilian vehicle was damaged during the attack.

Meanwhile, Russian strikes also caused casualties in Ukraine.

Authorities in the southern city of Zaporizhzhia said a Russian guided bomb hit a residential building, killing one person.

In the northeastern Kharkiv region, another Russian attack killed one person and set a postal terminal on fire, according to regional officials.

The latest attacks came as both Russia and Ukraine continued to intensify long-range drone and missile strikes deep inside each other's territory.