Ukraine’s capital Kyiv came under attack by Russian ballistic missiles early Monday morning, the country’s air force said, on the eve of a critical NATO summit in Turkey that US President Donald Trump plans to attend.

Explosions were heard across the city center in the early hours as the combined attack, also involving drones and cruise missiles, continues. At least two districts in the city reported fires or damage from debris, Kyiv Mayor Vitaliy Klitschko said in a statement on Telegram.

Shortly before the explosions, air raid sirens were activated throughout the city.

The attack came after Ukrainian President Volodymyr Zelensky warned Sunday that ⁠that ‌intelligence ⁠indicated Russia was “preparing a new massive strike.”

It also follows a ferocious Russian attack on Kyiv last Thursday killed at least 30 people, in what was the third deadliest assault on the Ukrainian capital since the start of the war.