Tatyana Kim, the co-founder and head of Wildberries, on Wednesday said warehouses had been attacked in Krasnodar and Nevinnomyssk, both in southern Russia.
Social media footage, verified by Reuters, showed a huge plume of smoke rising into the air in Krasnodar. The regional governor said a young woman had been killed and three other people were being treated in hospital.
Wildberries, often described as Russia's Amazon, is one of the country's biggest employers. Its shares are not publicly traded, but those of its rival Ozon were down 2.3 per cent on Wednesday afternoon, recovering somewhat from earlier lows, on concerns it too could become a target.
The attacks on massive Wildberries warehouses mark a new stage in Ukraine's campaign of deep strikes inside Russia to undermine Moscow's war effort and bring the conflict home to ordinary Russians.
Ukraine, whose own cities are under constant attack, says it is hitting companies and infrastructure that support the Russian military. President Volodymyr Zelenskiy on Wednesday described the latest targets as logistics hubs involved in supplying Russian forces with drone components and other equipment.
The Kremlin has denied that Wildberries handles military supplies. Russia has targeted Ukraine's logistics hubs as well as its energy system and power grid.
A previous strike by Ukrainian drones on Saturday killed eight Wildberries workers, sparked fires and disrupted the company's operations.
"There are no words to describe all the feelings and emotions caused by the attacks on ordinary people, on our employees, on all of us who are simply doing our jobs," Kim, the company's boss, said in a post on Telegram after the latest attacks.
Russian news agencies later quoted Kim as telling journalists that the company's insurance policies had no provision for acts of "terrorism and sabotage", but it was endeavouring to restore normal operations.
Kim said the company was providing help to sellers and seeking government help in terms of tax and other breaks.
The extent of the damage, and the impact for customers, was not immediately clear.
An e-commerce lobby group, AUREK, said it had asked the government to delay tax payments for six months for businesses that sustained losses from the attacks.
Wildberries started as an online shop reselling apparel from European catalogues. It has since expanded its product range and evolved into a marketplace that includes third-party vendors. Wildberries has not commented on the scale of the damage.
Online sales across Russia rose 28 per cent in 2025 to 11.5 trillion roubles ($A210 billion), according to the Association of Internet Trade Companies. Deputy Prime Minister Alexander Novak said sales of goods and services on digital platforms equated to around 8.5 per cent of GDP.