The New York Times says the total number of Ukrainian and Russian troops who have been killed or injured is nearing 500,000 since Russia's invasion began 18 months ago.

The article published on Friday quotes US officials as saying Russia's military casualties are approaching 300,000, which includes as many as 120,000 deaths and up to 180,000 injuries.

Ukrainian figures are put at close to 70,000 killed and up to 120,000 wounded.

The newspaper cites the difficulty in estimating casualty figures, saying Russia is believed to routinely undercount its war dead and injured, and Ukraine does not disclose official figures.

It says the "slaughter intensified" this year in eastern Ukraine and "has continued at a steady clip" as a Ukrainian counteroffensive "drags on."

It also cites a lack of rapid medical care on the frontline.

Ukrainian President Volodymyr Zelenskyy met Swedish Prime Minister Ulf Kristersson in Sweden on Saturday. Zelenskyy said the two leaders talked about the steps needed to make it possible for Ukraine to receive Sweden's Gripen fighter jets.

The Ukrainian president posted a video online, saying that Sweden's CV90 armored infantry fighting vehicle is "just what is needed at the front."

He said the two countries had agreed that production of CV90 vehicles will begin in Ukraine.