Russia claimed Wednesday it foiled a Ukrainian assassination attempt using drones against President Vladimir Putin, denouncing the alleged attack as a ‘’terrorist’’ act and promising retaliation.

Putin wasn’t in the Kremlin at the time of the nighttime attack and was working from the Novo-Ogaryovo residence, Kremlin spokesman Dmitry Peskov told Russia’s state news agency RIA Novosti.

There were no immediate details and no independent verification of the reported attack on the Kremlin, which Russia authorities said occurred overnight but presented no evidence in support of the claim. Nor did officials say why it took more than 12 hours to report the incident.

Ukraine presidential advisor Mykhailo Podolyak denied any involvement.

“Ukraine has nothing to do with drone attacks on the Kremlin,” he said. He said the claims would provide a pretext for Russia “to justify massive strikes on Ukrainian cities, on the civilian population, on infrastructure facilities” in coming days.

The alleged attack immediately prompted calls in Russia from pro-Kremlin personalities to carry out assassinations on senior leadership in Ukraine.

If true, the purported drone attack would be a significant escalation in the 14-month conflict, with Ukraine taking the war to the heart of Russian power.

Russia Says Drones Were Stopped

The Kremlin said Russian military and security forces stopped the drones before they could strike. Nobody was hurt, it said in a a statement.

The claims came as Ukrainian President Volodymyr Zelenskyy made an unannounced visit to Helsinki for talks with the prime ministers of five Nordic countries. He is trying to secure greater firepower for his country’s armed forces as they figure out how to dislodge Russian troops from occupied areas of Ukraine.

Both Putin and Zelenskyy move around under tight security.

Debris from the unmanned aerial vehicles fell on the grounds of the seat of Russia’s president but caused no damage, a statement on the Kremlin’s website said.

A video published overnight on a local Moscow news Telegram channel, filmed across the river from the Kremlin, appeared to show smoke rising over the buildings. It wasn’t possible to ascertain its veracity.

According to the text accompanying the video, residents at a nearby apartment building reported hearing bangs and seeing smoke at around 2:30 a.m. local time.

The Kremlin claimed the attack was planned to disrupt Victory Day, which Russia celebrates on May 9 to commemorate the Soviet victory over Nazi Germany in 1945. Foreign dignitaries are expected to attend the Moscow event.

Peskov said the parade would take place as scheduled.

Shortly before the news about the alleged attack broke, Moscow Mayor Sergei Sobyanin issued a ban on using drones in the Russian capital, with an exception for drones launched by authorities.

Sobyanin didn’t offer any reason for the ban, saying only that it would prevent the “illegal use of drones that can hinder the work of law enforcement.”

Zelenskyy made no comment in Helsinki, though he was due to attend a news conference there later in the day.

The Nordic countries — Finland, Sweden, Norway, Denmark and Iceland — have been among Kyiv’s strongest backers since Russia’s full-scale invasion of Ukraine in February 2022. Before the meeting with Zelenskyy in Finland’s capital, Nordic officials appeared ready to provide more aid as the war stretches into its 15th month.

“There is still an urgent need for military support to ensure that the Ukrainians stand as strong as possible in the fight against Russia,” Danish Prime Minister Frederiksen said in a statement.

Norwegian Prime Minister Jonas Gahr Støre, another of the summit attendees, said: “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 talks came a day after U.S. officials said Washington 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.

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.

Elsewhere, Russia used Iranian-made drones during its third attack on Ukraine’s capital city in six days.

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

Meanwhile, a massive blaze broke out at an Russian oil depot, local officials said Wednesday.

The 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 think Ukraine is targeting supply lines in the Russian rear while gearing up for a possible counteroffensive amid improving weather conditions and as it receives large amounts of weapons and ammunition from its Western allies.

Explosions also derailed a Russian freight train and hit a Russian airfield in recent days. Last weekend, a massive fire erupted at an oil depot in Crimea after it was hit by two of Ukraine’s drones, a Russia-appointed official said.

In anticipation of a Ukrainian counteroffensive, Russian forces are focused on destroying logistical routes and centers of Ukraine’s armed forces with long-range strikes, Kyiv military officials say.

At the same time, Russia plans to continue talks with the United Nations and other parties to an wartime agreement on facilitating Black Sea agricultural shipments, Kremlin press secretary Dmitry Peskov said ahead of talks on Friday.

Earlier Wednesday, Russian Foreign Ministry spokeswoman Maria Zakharova confirmed that a new round of consultations between Russia and the U.N. on access of Russian agricultural products and fertilizers to the world market would be held in Moscow.

Signed last July and renewed twice, most recently in March, the deal unblocked Ukrainian grain shipments that were held up in the country’s blockaded ports last year. The deal will expire on May 18 unless Russia agrees to its renewal.

In the latest Ukrainian civilian casualties, 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 didn’t 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.