European stocks started the week on a weaker footing, with the STOXX 50 falling 1% and the STOXX 600 losing 0.8%, as investors returned from the weekend to renewed geopolitical tensions in the Middle East and a sharp rise in oil prices. Iran and Israel exchanged fresh strikes, undermining an already fragile ceasefire and raising concerns that efforts to end the conflict may be stalling. The broad-based selloff weighed on most sectors, while energy stocks outperformed as crude oil prices surged nearly 4%.