KYIV, Ukraine (AP) -- A massive blaze broke out at an Russian oil depot, local officials said Wednesday, while the Kremlin's forces used 26 Iranian-made drones in another nighttime attack on Ukraine as the war stretched into its 15th month.
The developments came as Ukrainian President Volodymyr Zelenskyy made an unannounced visit to the Finnish capital, Helsinki, for a one-day summit with Nordic leaders, as he pushes Ukraine's Western allies to provide Kyiv with more military support.
The Nordic countries have been among Ukraine's strongest backers.
"The war is ... a turning point for our entire continent," said Norwegian Prime Minister Jonas Gahr Støre, one of the summit attendees. "Here in the north, we have a more unpredictable and aggressive Russian neighbor, and it is important that we discuss together how to face this new situation."
The oil depot erupted in flames in Russia's southern Krasnodar region, located east of the Russian-held Crimean Peninsula, according to Krasnodar Gov. Veniamin Kondratyev.
He didn't say what caused the fire, which was described as extremely difficult to put out. But some Russian media outlets said it was likely caused by a Ukrainian drone attack overnight. There was no official comment on that possibility.
Local residents heard an explosion shortly before the fire erupted, Russian news site Baza said.
Military analysts reckon Ukraine is targeting supply lines in the Russian rear as Kyiv gears up for a possible counteroffensive amid improving weather conditions and as it receives large amounts of weapons and ammunition from its Western allies.
Explosions have also derailed a Russian freight train and hit a Russian airfield in recent days. Analysts say the attacks may be perpetrated by Ukrainian saboteurs.
At the same time, anticipating a Ukrainian counteroffensive, Russian forces are focused on destroying logistical routes and centers of Ukraine's armed forces, Kyiv military officials say.
Meanwhile, explosions were heard in Kyiv and elsewhere during the night as Ukrainian air defenses shot down 21 of the Russian drones, Ukraine's Air Force Command said.
No damage or casualties were reported in the third attempt in six days by the Kremlin's forces to hit Kyiv.
But three people died and five were wounded when a supermarket in the southern Ukrainian city of Kherson came under fire on Wednesday.
According to Ukraine's Ministry of Internal Affairs, the attack on the "only operating hypermarket in Kherson" happened at around 11 a.m. local time.
A round-the-clock curfew is to be introduced in Kherson from 8 p.m. on Friday through 6 a.m. on Monday, Kherson Gov. Oleksandr Prokudin announced.
"During these 58 hours, it is forbidden to move around or stay on the streets of the city. Also, the city will be closed for entry and exit," Prokudin said.
The measure is necessary, he said in a video on social media, "so that law enforcement officers can do their job and not put you in danger," but did not provide further details.
Both Russia and Ukraine reportedly have experienced ammunition shortages after a winter of long-range shelling and missile strikes as the conflict became bogged down in a war of attrition.
Ukraine's government has been pressing its allies to give it more as officials consider when and how they might start trying to drive Russian forces out of the Ukrainian territory they have occupied.
The U.S. plans to send Ukraine about $300 million in additional military aid, including an enormous number of artillery rounds, howitzers, air-to-ground rockets and ammunition, U.S. officials said late Tuesday.
The new package includes Hydra-70 rockets, which are unguided rockets that are fired from aircraft. It also includes an undisclosed number of rockets for the High Mobility Artillery Rocket Systems, or HIMARS, mortars, howitzer rounds, missiles and Carl Gustaf anti-tank rifles.
The weapons will all be pulled from Pentagon stocks, so they can go quickly to the front lines, according to the officials who spoke on condition of anonymity because the aid has not yet been formally announced.
New Zealand also said it was increasing its support for Ukraine by adding another year to the deployment of about 100 military personnel who, among other tasks, have been helping train Ukrainian troops in Britain on operating howitzers.
New Zealand Prime Minister Chris Hipkins said it will also donate an additional $3.3 million toward Ukrainian humanitarian, refugee and legal justice efforts. He said New Zealand has spent about $50 million on financial and military support to Ukraine since the war began.