European stocks started the week on a cautious note, with both the STOXX 50 and the STOXX 600 trading flat to lower as oil prices climbed following renewed military strikes involving the US and Iran. The technology sector came under pressure after South Korea's SK Hynix plunged 15% in Seoul, its largest one-day decline on record, as investors locked in profits following a 13% surge in its US-listed American depositary receipts during their trading debut on Friday, while also reassessing the outlook for AI-driven demand. Among European tech names, ASML Holding (-2%) and Infineon Technologies (-3%) were among the session's weakest performers.