KYIV, Ukraine (AFP) — Drones attacked the Ukrainian capital early Monday morning, the Kyiv city military administration said, urging people to heed air alerts.

"The enemy is attacking the capital," the administration posted on Telegram.

"At the moment, 9 enemy UAVs (unmanned aerial vehicles) have already been shot down in the airspace of Kyiv."

It added that the Russian forces were using barrage ammunition from "Shaheds," Iran-made weapons that have pummelled the capital in recent weeks.

The city's civil administration announced an initial air alert at 1:56 a.m. which lasted for just over three hours. A second siren at 5:24 a.m. was called off within a half hour.

Kyiv mayor Vitali Klitschko confirmed on Monday that "explosions" had occurred in the capital.

"Several explosions were heard in the Solomianskyi and Shevchenkivskyi districts of the capital," he said. "All services work on the ground. More details later."

Ukraine has been subjected to frequent and deadly aerial attacks in the 10 months since Russia's invasion in February.

After a series of key battlefield setbacks and lost territory this summer and autumn, Moscow pivoted strategies and stepped up its aerial campaign.

Russia's defense ministry says its strikes are targeting Ukraine's military and energy facilities, while also disrupting "the transfer of weapons and ammunition of foreign production."