North Sea oil climbs to just over $102.35 per barrel in futures trading for June, while U.S. WTI rises to $105.55 in futures trading for May.
Thus, prices have climbed 7.7 percent and 9.2 percent, respectively, compared to Friday's close.
Before the U.S. and Israel's war against Iran began on February 28, oil cost around $70.
On Friday, prices fell on hopes for this weekend's peace negotiations between the U.S. and Iran, but when those collapsed, U.S. President Donald Trump issued further threats.
One of the stumbling blocks is that Iran can block transport through the Strait of Hormuz, where about a fifth of the world's oil normally passes.
The rising oil prices are hitting economies around the world hard.
