A major oil terminal near Russia's second city of St Petersburg came under attack overnight from Ukrainian forces, President Volodymyr Zelensky confirmed.

He called the site critical infrastructure that helps fund Russia's war effort. Ukraine further reported strikes against a significant naval base in the same region.

St Petersburg Governor Aleksandr Beglov described the incident as a massive drone assault and confirmed the oil terminal was struck, while noting zero casualties.

Ukraine has increased long-range drone operations against Russian energy assets in recent weeks, triggering broad fuel shortages. Kyiv asserts that nearly 43 percent of Russia's oil refining capacity is now disabled, although independent verification is still pending.

Ukraine maintains that Russian oil and gas installations qualify as legitimate targets because Moscow depends on fossil fuel exports to sustain its campaign.

Russian President Vladimir Putin, who recently acknowledged fuel shortages triggered by Ukrainian strikes, enacted new legislation on Saturday designed to strengthen domestic fuel supplies.

Putin began the full-scale invasion of Ukraine in February 2022.

Zelensky stated on Saturday that the locations struck lie roughly 850km from the Ukrainian border.

Damage assessments remain preliminary, yet video released by the president captured a drone approaching its target followed by a thick plume of black smoke rising from the site.

The BBC independently confirmed that the St Petersburg oil terminal was hit.

Ukraine's military labeled the terminal one of Russia's largest, with an annual output capacity of 12.5 million tonnes of petroleum products.

The military also reported strikes on the Russian Baltic Fleet's main base in Kronstadt.

Russia has issued no public response to these claims.

Governor Beglov said 72 Ukrainian drones were intercepted over St Petersburg and the Leningrad region.

He advised residents to remain indoors while the threat persisted and warned that mobile internet services could face disruptions.

St Petersburg is home to more than five million people.

In a separate statement, Ukraine's military rejected claims that the eastern town of Kostyantynivka has fallen entirely under Russian control.

Military spokesman Maj Andriy Kovalyov told the BBC that Ukrainian defence forces still hold the town.

He acknowledged limited Russian infantry infiltrations but said such units were being detected and eliminated.

His remarks followed Putin's assertion a day earlier that Russian forces had secured Kostyantynivka in June, an assertion made without supporting evidence.

Later on Saturday Zelensky posted on Telegram that if Kostyantynivka were truly under Russian control, Putin should have no difficulty meeting him there to pursue diplomatic solutions, yet the Russian leader would not cross the front line because the reality differs from his statements.

Kostyantynivka forms part of Ukraine's fortified defensive line in the Donetsk region, much of which remains under Russian occupation.

Russia's defence ministry reported downing more than 500 Ukrainian drones and missiles overnight and into Saturday morning.

It framed the Ukrainian strikes as an attempt by Zelensky to divert attention from recent Russian attacks on Kyiv and alleged Ukrainian setbacks near Kostyantynivka.

The ministry warned that Ukrainian strikes on Russian civilian sites would not go unanswered.