Kyiv, Ukraine - At least 10,000 civilians, including more than 560 children, have been killed in Ukraine since Russia's full-scale invasion began 21 months ago, the UN said.

However, since many bodies had not yet been identified, the actual death toll was likely to be "considerably higher," the Office of the UN High Commissioner for Human Rights (OHCHR) announced on Tuesday in Geneva.

More than 18,500 civilians had been injured, OHCHR reported.

"Ten thousand civilian deaths is a grim milestone for Ukraine," said Danielle Bell, head of the UN mission in Ukraine.

Ukraine conflict Ukraine army commander says situation "worsened" as Russia continues offensive

After another night of Russian aerial attacks, Britain's Ministry of Defense warned that Russian armed forces could be preparing for a new winter cruise missile campaign against Ukraine's energy infrastructure.

The Russians have been holding back on firing cruise missiles for almost two months, which the ministry suggests was to "build up a substantial stock of these weapons."

Attacks on major Ukrainian cities, including Kyiv, have increased in recent weeks as Moscow appears set to escalate its aerial onslaught.

With talk of a stalemate on the battlefield increasing, the US has recently recommitted itself to military support for Ukraine, with a new $100-million aid package confirmed on Monday.