New Delhi: An air raid siren sounded across all Ukraine's regions on Thursday after a fresh wave of Russian missiles strike several big cities.

Presidential adviser Oleksiy Arestovych shared on social media that more than 100 missiles had been launched toward Ukrainian cities in "several waves".

Blasts were also heard in the cities of Kharkiv, Odesa and Zhytomyr. At least two explosions were reported in Kyiv, but it was unclear if they were the result of missile attacks or air defences, reported BBC.

Maksym Marchenko, Odesa regional leader, said in a statement that Russia has carried out a “massive missile attack” on Ukraine.

Here's what is happening in Ukraine-

1. Power cuts were announced in the Odesa and Dnipropetrovsk regions, aimed at minimising potential damage to the energy infrastructure, news agency Reuters reported.

2. "After the night attack of self-exploding drones, the enemy is attacking Ukraine from various directions with air and sea-based cruise missiles from strategic aircrafts and ships," CNN quoted the Ukrainian Air Force as saying.

3. “Air defence is working over the region now,” Marchenko said, calling on residents to stay in shelters, CNN reported.

4. Moscow has repeatedly denied targeting civilians, but Ukraine says its daily bombardment is destroying cities, towns, and the country's infrastructure from power to medical.

5. Earlier, Ukraine's southern command had issued a warning that Russian force were preparing to launch up to 20 missiles from positions in the Black Sea.

6. Ukraine's recently liberated southern city of Kherson has remained under constant bombardment from Russian forces which had retreated to the east bank of the river when the city was retaken in a major victory for Ukraine last month.

Recently, Ukraine has been subjected to dozens of Russian strikes, which have repeatedly resulted in power outages across the country.