Warehouses belonging to Russia's second-largest online retailer have been hit by a wave of Ukrainian drone strikes.

Ozon said its logistics facilities in the southern regions of Krasnodar, Dagestan, Stavropol and Adygea were on fire and several people had been injured following overnight strikes.

Ukraine has for weeks struck sites belonging to Wildberries, the country's biggest online retailer, describing the firm as a legitimate target because it supplied components to the military, which Moscow denies.

Russian President Vladimir Putin said on Saturday that Ukraine had opened "Pandora's box" by striking economic targets and that Russia would hit back at Kyiv's "most sensitive economic sectors".

Russia has targeted Ukraine's civilian infrastructure since launching its full-scale invasion in 2022, and recent Russian attacks have hit Ukrainian warehouses and cargo terminals.

Both Russia and Ukraine deny deliberately targeting civilians.

Ozon said "a fire broke out" at a logistics centre in Makhachkala, in the southern region of Dagestan, following a drone attack at around 05:00 local time (02:00 GMT) on Monday.

The company said earlier that a "major fire" was burning at one of its logistics centres in the city of Krasnodar, 700km (435 miles) to the east of the Dagestan site.

Russia's defence ministry said three children had been killed in Krasnodar following a Ukrainian drone attack. Russia's children's rights commissioner Maria Lvova-Belova said they were aged 13, 15 and 16, while six more children had been taken to hospital.

Meanwhile, Ozon workers in Adygeysk, in the Adygea region, and Nevinnomyssk, in the Stavropol region, have been evacuated.

Videos posted on social media of the Ozon attacks have been verified by the BBC. One shows a drone hitting a warehouse in the Orenburg region, while another shows a large plume of smoke and flames rising from its warehouse in Dagestan.

Shares in Ozon fell by as much as 12% on the Moscow Exchange on Monday morning, while shares in its major shareholder, private equity firm AFK Sistema, fell by almost 13%.

When asked on Monday whether the Russian government would provide state support to Ozon, the Kremlin said it was "working with business representatives to develop various options for providing support in this difficult situation".

The overnight strikes comes a day after Ozon's site in the Samara region was hit. The company said a number of its workers had been injured.

Following that strike, Ukraine's defence ministry said on Saturday: "Systematic strikes on dual-use goods storage centres complicate the enemy's logistics and negatively affect the Russian economy as a whole.

"After Ukrainian units hit 15 of the largest logistics hubs of Wildberries, it was Ozon's turn."

Meanwhile, in Ukraine's Odesa region, overnight strikes targeted food storage facilities and energy infrastructure leading to five people being injured, the region's head Oleg Kiper said on Telegram.

Founded in 1998, Ozon is one of Russia's first online retailers. The company is second only to Wildberries in terms of scale and presence, with its pick-up posts and delivery boxes stationed across the country.

Both the Ozon and Wildberries logos are often seen together in Russia at shared pick-up points.

The targeting of these online retailers has had the effect of bringing the war closer to ordinary Russians.

Both companies have been described as "Russia's Amazon" and it is estimated that they are used by 85-90% of Russia's economically active population.

In many remote places lacking accessible shops, Russians depend on them for much of their clothes and household appliances.

But unlike Amazon, which sells goods directly alongside its marketplace business, Wildberries and Ozon act almost entirely as marketplaces, connecting independent sellers with buyers across Russia, storing and delivering their goods and handling payments.

This means many of the losses incurred in the attacks have been borne by those businesses.

The Kremlin has denied that online platforms are used for army supplies.