The Ukrainian government has warned that six Russian Black Sea ports are in a "war risk area," including Novorossiysk in the Krasnodar region.

A US think tank, the Institute for the Study of War, said on Saturday that Ukrainian officials had issued a notice to mariners that Ukraine may strike vessels near the Russian ports.

The institute called the announcement a "measured response" to the continued Russian strikes against Ukraine's main port of Odesa since July 17.

The Ukrainian Air Force said on Sunday that Russia launched a multi-wave overnight attack using cruise missiles and Iranian-made drones. It said the Ukrainian side intercepted 30 of the 40 missiles and destroyed all the drones.

Ukrainian President Volodymyr Zelenskyy said on social media on Saturday that a Russian bomb hit a blood transfusion center in Kupiansk in the Kharkiv region, and there were reports of dead and wounded. He added, "This war crime alone says everything about Russian aggression."