The U.N. human rights office said on Friday it had confirmed 331 civilians have been killed and 675 injured in Ukraine since Russia's invasion began on February 24, adding that the real toll was likely much higher.

The toll, through to midnight on Thursday, rose from 249 in its previous report from a day earlier. Among the 331 killed were 19 children, the UN rights office said.

Most of the victims were killed by explosive weapons such as shelling from heavy artillery, multi-launch rocket systems, and missile and airstrikes, according to the rights office, which has monitors in Ukraine.

Meanwhile, days into its widely denounced invasion of Ukraine and Russia has finally confirmed that it has seen losses in its ongoing attack, with the country's Defense Ministry announcing Wednesday that 498 Russian troops had died and 1,597 more had been injured since the country began what it has called a "special military operation."

Russian Defense Ministry spokesman Igor Konashenkov also claimed that 2,870 Ukrainian troops have also been killed and around 3,700 injured.

More than 500 Ukrainian soldiers, he contended, had been captured.