Ukraine has stepped up drone attacks on Russian oil refineries and exporting infrastructure, striking the most important sector of President Vladimir Putin's economy to show it can fight back as the United States seeks to broker a peace deal.

Crude oil futures started the week with solid gains as expectations fade for a Russia-Ukraine peace and rise that the US will increase sanctions, while tight diesel supplies support prices.

A dramatic rise in Ukrainian attacks on Russian oil refineries has sent gasoline prices in Russia to record highs, despite the government banning petrol exports to cope with the crunch.