Ukraine has lost more than 40% of the territory in Russia's Kursk region that it rapidly seized in a surprise incursion in August as Russian forces have mounted waves of counterassaults, a senior Ukrainian military source said.

Oil futures settled higher on Friday, with the U.S. crude benchmark up by more than 6% for the week as traders monitor escalating tensions between Ukraine and Russia, which is among the world’s biggest oil producers.

Oil prices rose in early European trade and were on track for weekly gains of more than 5% as escalating tensions between Russia and Ukraine kept energy markets on edge.