European stock markets closed lower Monday as fighting between the US and Iran reignited over the weekend, triggering a jump in oil prices.

The Stoxx Europe 600 dropped 0.6%, Germany's DAX 40 fell 1.1%, France's CAC 40 declined 0.6%, and the Swiss Market Index lost 0.8%.

Brent crude rose 2.9% to $90.65 a barrel, and West Texas Intermediate rose 2.6% to $85.54 a barrel.

In Germany, the Federal Statistical Office estimated that inflation for August, as measured by the change in the consumer price index, will be 2.9% on the year and 0.2% on the month, while energy prices climbed 10.5% from a year earlier.

In corporate news, Aon agreed to acquire USI Insurance Services from KKR and other shareholders for $17 billion. The transaction will be funded with new debt raised across a range of maturities.

Shares of Aon fell 1.8% in Frankfurt.

Eni is working with Venezuelan authorities to help revive the country's energy sector, Bloomberg reported Saturday.

Eni also entered Uruguay's offshore sector through an agreement with MIWEN, a wholly owned subsidiary of YPF, and ANCAP to join the OFF-5 exploration block, following regulatory approval.

Shares of the Italian oil and gas major increased 1.9% in Milan.

Stellantis named Arnaud Belloni as chief executive of its Fiat, Abarth, and Lancia brands, as well as chief marketing officer for Europe.

Shares of Stellantis advanced 1.9% in Paris.