Crude oil futures hit a new seven-month high in Tokyo on Monday as the killing of a top Iranian general in a US airstrike heightened tensions in the Middle East.
Key crude futures opened above 43,300 yen, or 400 dollars, per kiloliter. In December, they were trading between 38,000 yen and almost 43,000 yen.
Market sources say investors are worried about a possible drop in the supply of crude oil from Middle East oil-producing nations due to the tensions.
They say if the impact begins to be actually felt in the production and transport of oil in the region, the prices would rise further.
They say markets are closely watching to see how Iran will react.