Russia and Ukraine have both suffered high numbers of military casualties since the invasion started 20 months ago. The numbers keep rising amid fierce fighting in eastern and southern Ukraine.

Russia's military is apparently deploying additional troops and ramping up its offensive around Avdiivka, a stronghold in Donetsk for Ukrainian forces, in a bid to seize control of the area.

The UK defense ministry put the number of Russian personnel who have been killed or permanently wounded since the invasion began on February 24 last year at 150,000 to 190,000.

A high-ranking Russian government official this month revealed that more than half of seriously wounded soldiers ended up having limbs amputated.

The UK defense ministry on Monday said Russia will need to allocate more money to "fund payments and healthcare costs for the mounting numbers of wounded soldiers and the families of those killed in the conflict." It added that, "continued increases in military spending would force the Russian government to make difficult decisions about how to fund the war."

Ukraine, too, has lost many of its soldiers, as the country continues its counteroffensive.

The New York Times in August quoted US officials as saying Ukraine had suffered close to 70,000 killed since the onset of the invasion.

A church in the western Ukrainian city of Lviv on Monday hosted a funeral service for three fallen Ukrainian soldiers.

After Russia launched the invasion, a cemetery in the city set aside a section of its grounds for soldiers who lost their lives in the conflict. Officials say the number of graves there increased to 536 as of Monday, from around 300 in March.

One of the attendees at the funeral said Ukraine is paying an extremely high price. She said her country could eventually suffer enormous casualties and may not be able to withstand them. She called for more weapon supplies and aid to Ukraine.