Ukraine's air force says nine Russian warplanes were destroyed in large explosions at an air base in Crimea earlier this week.
The comments came amid speculation the explosions were the result of a Ukrainian attack which would represent a significant escalation in the war.
Russia earlier denied any aircraft were damaged — or that any attack took place — saying the blasts happened when munitions at the Saky air base caught fire and blew up.
On Facebook, Ukraine's air force posted what it said were photos of the air base before and after the incident.
In one photo, what appear to be swept-wing jet fighters are seen parked up in blast shelters.
In another, which appears to show the same area, some of the aircraft appear to be have been destroyed.
The photos have not been independently verified.
Ukrainian officials have stopped short of publicly claiming responsibility for the explosions, while also underscoring the importance of the peninsula that Moscow annexed eight years ago.
In his nightly video address several hours after the blasts, Ukrainian President Volodymyr Zelenskyy vowed to retake the peninsula.
"This Russian war against Ukraine and against all of free Europe began with Crimea and must end with Crimea — its liberation," he said.
On Wednesday, Russian authorities sought to downplay the blasts, saying all hotels and beaches were unaffected on the peninsula, which is a popular tourist destination for many Russians.
The explosions, which local authorities said killed one person and wounded 13, sent tourists fleeing in panic as plumes of smoke towered over the nearby coastline. They knocked out windows and caused other damage in some apartment buildings.
Russian warplanes have used Saky to strike areas in Ukraine's south on short notice, and Ukrainian social networks were abuzz with speculation that Ukrainian-fired long-range missiles hit the base.
Officials in Moscow have long warned Ukraine that any attack on Crimea would trigger massive retaliation, including strikes on "decision-making centres" in Kyiv.
The base, on the Black Sea peninsula that dangles off southern Ukraine, is at least 200 kilometres away from the closest Ukrainian position — out of the range of the HIMARS missiles supplied by the United States.
The Ukrainian military has successfully used those missiles, which have a range of 80 kilometres, to target ammunition and fuel depots, bridges and other targets in Russian-occupied territory. HIMARS could also fire longer-range rockets, with a range of up to 300 kilometres, that Ukraine has asked for.
US authorities have refrained from providing them thus far, fearing that doing so could provoke Russia and widen the conflict.
Ukrainian military analyst Oleh Zhdanov said the Ukrainian forces could have struck the Russian air base with a Ukrainian Neptune anti-ship missile, which has a range of about 200 kilometres, and could have been adapted for use against ground targets and potentially fired from Ukrainian positions near Mykolaiv, north-west of Crimea.
"[Officially] Kyiv has kept mum about it, but unofficially the military acknowledges that it was a Ukrainian strike," Mr Zhdanov said.
If Ukrainian forces were, in fact, responsible for the blasts, it would be the first known major attack on a Russian military site in Crimea, which the Kremlin annexed in 2014.
A smaller explosion last month at the headquarters of Russia's Black Sea Fleet in the Crimean port of Sevastopol was blamed on Ukrainian saboteurs using a makeshift drone.
Shelling kills 13 people in Dnipropetrovsk
Russian shelling hit areas across Ukraine on Tuesday night into Wednesday, including the central region of Dnipropetrovsk, where 13 people were killed and 11 others were wounded, according to the region's governor Valentyn Reznichenko.
Mr Reznychenko initially said there were 21 fatalities, with 11 killed in the district of Nikopol and 10 in Marhanets, but later clarified that 13 people had died.
Dozens of residential buildings, two schools, a hostel, a concert hall and several administrative buildings were also damaged by the shelling. The attack also damaged power lines, leaving several thousand people without electricity.
"It was a terrible night," Mr Reznichenko said.
"It's very hard to take bodies from under debris. We are facing a cruel enemy who engage in daily terror against our cities and villages."
Russia denies targeting civilians in what it calls its "special military operation" in Ukraine.
Meanwhile, Russian forces continued shelling the nearby city of Nikopol, across the Dnieper River from the Russia-occupied Zaporizhzhia nuclear power plant, Europe's largest.
Mr Zelenskyy called the shelling "Russian nuclear terror" that warranted more international sanctions, this time on Moscow's nuclear sector.
"There is no such nation in the world that could feel safe when a terrorist state fires at a nuclear plant," he said.
However, the Russian-installed authority in the area said it was Ukraine that hit the site.
Ukraine and Russia have regularly accused each other of shelling the power station, stoking international fears of a catastrophe.
In its daily briefing on Wednesday, Russia's Defence Ministry said Russian forces destroyed a German-supplied Gepard anti-aircraft system being used by Ukrainian forces in the Mykolaiv region.
The ministry also said it had shot down three Ukrainian warplanes in the Mykolaiv region, as well as seven HIMARS missiles in the neighbouring Kherson region.
The ministry's reports could not be independently verified by Reuters.