Residents in parts of south-east Moscow reported a light drizzle that left black marks on clothing and other surfaces after a refinery was struck during a major Ukrainian drone attack. While city authorities denied reports of "oil rain", Moscow's official Telegram channel advised people in the affected district to keep their windows closed and urged families with children, elderly residents and those with asthma to leave the area.The reports emerged after Ukraine launched its largest drone attack on Russia since the start of the full-scale war, targeting Moscow and other regions with nearly 200 drones aimed at the Russian capital. The assault damaged a refinery in south-east Moscow, sparked fires and left 17 people injured in the Moscow region, according to regional governor Andrei Vorobyov.Refinery strike sparks fires and heavy smokeThe Kapotnya refinery in south-east Moscow was struck for the third time in a month and for the second time within the same week. Thick black smoke rose above the facility as fires broke out following the attack.Videos circulating on social media showed a major explosion at the site, with the top of a large storage silo blown off and the roof of an oil tank thrown high into the air. A nearby shopping centre also caught fire, reportedly after being struck by falling drone debris.In another verified video, a drone was seen crashing into the upper floors of a high-rise building, scattering glass and debris into the courtyard below.Residents describe black specks after attackLocals in the affected area said a fine drizzle left dark residue on clothing. One resident told the BBC that black spots appeared on her clothes shortly after she stepped outside, while a friend's jacket was similarly covered in dark specks.Additional footage verified by the broadcaster showed a dark oily coating on the surface of a car park, although the ground beneath parked vehicles appeared unaffected.Hundreds of drones intercepted across RussiaRussia's Defence Ministry said almost 1,000 drones and four Ukrainian cruise missiles were intercepted and destroyed across the country within a 24-hour period. The ministry also reported that 555 drones were shot down nationwide.Moscow Mayor Sergei Sobyanin said 180 drones were intercepted around the capital alone. Russian state news agency TASS described the assault on Moscow as one of the largest attacks on the city this year.An oil depot in the southern Rostov region was also struck. Authorities said one person was killed in the attack.Air travel disrupted as restrictions imposedThe drone assault led to temporary closures at all four Moscow airports. More than 500 flights were either cancelled or delayed as authorities responded to the security threat.Although Russian authorities have prohibited the publication of images showing the aftermath of drone strikes, numerous videos appeared on social media depicting drones flying over Moscow in daylight and explosions in industrial areas on the city's outskirts.Kyiv links strike to earlier attack on KyivUkrainian President Volodymyr Zelensky confirmed the refinery attack and said it was a response to a Russian strike on Kyiv the previous week that set fire to the Pechersk Lavra monastery."We don't want this war and have never wanted it," Zelensky said. "But if Ukraine burns, your Moscow will burn too."Ukraine's military also said its forces struck an oil depot in Russia's Rostov region and targeted two bridges as part of efforts to disrupt Russian logistics.Russia vows intensified retaliationRussian Foreign Minister Sergei Lavrov responded by warning that Russia would carry out attacks on Ukraine "on a mass scale", adding that he had long believed words alone were insufficient.Military analysts have noted that Ukraine frequently deploys large numbers of reconnaissance and decoy drones to assess air defence coverage and identify vulnerabilities before launching primary strike operations.