An overnight Ukrainian drone attack on an oil depot near the Russian Black Sea resort of Sochi ignited a raging fire, as the two countries traded strikes at the end of one of the deadliest weeks in Ukraine in recent months.

More than 120 firefighters worked to put out the blaze, said the regional governor, Veniamin Kondratyev, as emergency officials reported a fuel tank with a capacity of 2,000 cubic metres (70,000 cubic feet) had burned before it was extinguished.

Drone wreckage hit an “oil tank, which caused a fire”, Kondratyev said on the Telegram messaging app. Sochi, which hosted the 2014 Olympic Winter Games, is about 250 miles (400km) from the Ukrainian border.

Video clips on social media showed huge black pillars of smoke pouring out from the facility.

Russia’s civil aviation authority temporarily halted flights at Sochi airport, as the Ukrainian president, Volodymyr Zelenskyy, announced fresh plans for a prisoner exchange.

Kyiv has repeatedly pounded infrastructure in Russia that it sees as key to Moscow’s war effort but attacks on Sochi have been relatively rare.

The strike came as a Russian missile hit a residential area in the southern Ukrainian city of Mykolaiv, according to the state emergency services, wounding at least seven people. Officials in nearby Kherson said Russia again bombed a crucial bridge, causing significant damage.

In Russia’s Voronezh region, authorities said four people were hurt in a separate Ukrainian drone strike.

As Moscow rebuffs repeated calls by the US president, Donald Trump, for a ceasefire, a Russian drone and missile attack on Kyiv on Thursday killed 31 people, including five children, and wounded more than 150 in one of the worst single-day tolls in several months.

The EU foreign policy chief, Kaja Kallas, described the assault as “depraved” and posted a picture of the bloc’s flag at half mast.

Zelenskyy has been appealing to allies for more air defence systems to rebuff the Russian escalation.

On Friday, Germany said it would soon start delivering two more US-made Patriot launchers in addition to three Patriot systems already delivered to Ukraine since the start of Russia’s full-scale invasion in February 2022.

Trump on Tuesday gave the Russian president, Vladimir Putin, a shorter deadline of 8 August for peace efforts to move forward, as attacks continue unabated. The US leader has threatened new economic sanctions if progress is not made – a measure long demanded by Kyiv and backed by EU powers.

Zelenskyy said on Sunday that Ukraine and Russia had agreed to exchange 1,200 prisoners after their latest round of talks in Istanbul in July.

“There is an agreement to exchange 1,200 people,” he wrote on X, saying the lists of individuals to be swapped was still being determined to “unblock the return of our civilians”.

“Preparations for a new meeting” were also under way, Zelenskyy said.

Each of the three rounds of Ukrainian-Russian negotiations this year has resulted in prisoner exchanges but yielded no breakthrough in reaching an end to the fighting.

The Russian government did not immediately comment.

The Ukrainian air force said on Sunday that Russia had launched 76 drones and seven missiles against Ukraine overnight. It said it destroyed 60 drones and one missile, but 16 others and six missiles hit targets across eight locations.

Early in the war, the Mykolaiv region faced frequent Russian artillery strikes and aerial attacks. Even after Russian forces were pushed back in late 2022, drones and missiles have remained a constant danger.

The Russian defence ministry said its air units intercepted 93 Ukrainian drones overnight, including one over the Krasnodar region and 60 over the Black Sea.

Ukrainian authorities said at the weekend that they had targeted other key sites for Russia’s energy and defence sectors in retaliation for the recent deadly strikes on Ukrainian cities.

The week also brought political turbulence for Kyiv, after nationwide protests prompted parliament to restore the independence of Ukraine’s anti-corruption agencies.

Over the weekend a Ukrainian lawmaker and other officials were arrested after those agencies unearthed an alleged wide-ranging bribery scheme linked to the purchase of drones and other weapons systems.

Pledging “zero tolerance” for corruption, Zelenskyy himself announced the arrests on X. The scheme is believed to have hiked prices by up to one-third in state contracts with suppliers.

A previous, hotly contested bill that MPs passed in July with support from Zelenskyy’s Servant of the People party, which had made the fight against sleaze its calling card, had stripped powers from the independent national anti-corruption bureau, known as Nabu, and the specialised anti-corruption prosecutor’s office, Sapo.