Russia launched overnight air attacks on Ukraine’s south and east using drones and possibly ballistic missiles, Ukraine’s Air Force and officials said early on Tuesday.

A fire broke out at one of the “facilities” in the port of Mykolaiv late on Monday, the city mayor said. The port city provides Ukraine with access to the Black Sea.

“It’s quite serious,” Mayor Oleksandr Senkevich said on the Telegram messaging app of the fire, adding that more detail will come in the morning.

The southern port of Odesa and the Mykolaiv, Donetsk, Kherson, Zaporizhzhia and Dnipropetrovsk regions were under threat of Russian drone attacks, the Air Force said on the Telegram messaging app.

It added that Russia may be using ballistic weaponry to attack the regions of Poltava, Cherkasy, Dnipropetrovsk, Kharkiv and Kirovohrad.

Reuters could not independently verify the reports.

Air raid alerts blared in many Ukrainian regions for hours, before being called off at around 04:30 a.m. local time (0130 GMT).

Oleh Kiper, the head of the Odesa region’s military administration, said air defence systems there were engaged in repelling several waves of Russian drone attacks.

Serhiy Bratchuk, a spokesperson for Ukraine’s Odesa military administration, said on the Telegram messaging app that details of the attack will come later in the morning.

“Thank you all for your endurance,” he said.

There was no immediate comment from Russia on the attack.

Early on Monday, a blast knocked out the Crimean Bridge linking Russia to the Crimean Peninsula, which Moscow annexed from Ukraine in 2014, in what Moscow called a strike by Ukrainian sea drones and vowed retaliation.