Benchmark Brent crude oil futures rose past $100 a barrel, breaching the symbolic barrier for the first time since July 24 as the ongoing conflict in the Middle East escalated, Reuters reported.
Oil majors in the UK advanced, with BP and Shell rising 1.5% and 1% respectively, with energy stocks hitting a more than four-month high.
Heavyweight banks were the biggest drag, with HSBC down 1.2%, Barclays off 1.6% and Lloyd Banking sliding 1.3%.
"Brent crude pushing above $100 a barrel has had a psychological effect on the market, pushing a hypothetical inflation worry gauge to ‘serious’ status and dragging down financial assets," said Dan Coatsworth, head of markets at AJ Bell.
Investors are closely watching a key US inflation report and economic growth data in the UK this week that could influence interest rate expectations from central banks.
Markets are pricing in a 60% chance the US Federal Reserve will hike rates next week but widely expect the Bank of England to stand pat on rates, per LSEG data.
Among stocks, Burberry slipped 2.4% after HSBC downgraded the stock to "hold" from "buy". It weighed down the personal goods sector.
Asset manager Aberdeen rose 2.2% after naming Torbjörn Magnusson, the former chief executive of Nordic insurance giant Sampo, as its chair-designate and non-executive director.
Among the midcaps, polymer maker Victrex topped the index with a 14.7% rise after raising its annual underlying profit before tax forecast.
Eastern Mediterranean-focused gas producer Energean rose 3.9% after posting a 45% jump in first-half profit.