UNITED NATIONS, Oct 10 (AFP) - Ukraine denounced Russia as a "terrorist state" at an urgent United Nations General Assembly meeting on Monday (Oct 10) following its neighbour's latest attacks, as Western powers sought to underscore Moscow's isolation.

The UN called the debate to discuss Russia's declared annexation of four partly occupied Ukrainian regions, but the debate was overshadowed by strikes on Kyiv and other cities in one of the most punishing assaults on Ukraine in months.

"Russia has proven once again that this is a terrorist state that must be deterred in the strongest possible ways," said Sergiy Kyslytsya, Ukraine's ambassador to the UN in his opening remarks, adding his own immediate family had come under attack.

"Unfortunately, you can hardly call for a stable and sane peace as long as an unstable and insane dictatorship exists in your vicinity," he added, telling member states at least 14 civilians were killed and 97 wounded in the attacks.

Responding, Vasily Nebenzya of Russia did not directly address the missile strikes, but defended his country's annexation of Ukrainian regions.

"We are being accused when we are trying to protect our brothers and sisters in eastern Ukraine," he said.

Ahead of the General Assembly session, and with tensions at a boiling point, UN chief Antonio Guterres described Russia's attacks as an "unacceptable escalation of the war," his spokesman said.

US President Joe Biden, meanwhile, condemned the strikes in stark terms, saying they "demonstrate the utter brutality" of Putin's "illegal war".

Russian President Vladimir Putin vowed even more "severe" retaliation after the recent explosion that damaged a key bridge in Moscow-annexed Crimea.