The pan-European STOXX 600 was down 1.2% at 543.54 points as of 0707 GMT. The benchmark is on track to log a fifth session in the red, setting it up for a weekly decline.
Israel launched strikes against Iran on Friday, hitting nuclear facilities and ballistic missile factories, to prevent Tehran from building an atomic weapon. Iran retaliated by launching 100 drones.
The tensions add to caution in global financial markets as they grapple with the impact of U.S. President Donald Trump‘s tariff policy.
The heightened tensions in the oil-rich Middle East sent prices of the commodity soaring, last up over 7%, weighing most heavily on airlines.
The travel and leisure sector was down 3.1%. British Airways owner ICAG tumbled 4.8%, Lufthansa down 4.6% and EasyJet dropped 4.3%. Cruise operator Carnival’s London-listed shares slipped 5%. On the flip side, energy stocks soared, with Shell and BP up 1.9% each.
Shares of defence companies were also higher, with France’s Dassault Aviation up 1.3% and Italy’s Leonardo up 2.3%.