Oil prices jumped on Monday on escalating sanctions against Russia over its invasion of Ukraine, which in turn led President Vladimir Putin to put his country's nuclear deterrent on high alert.
Brent jumped back above $100 a barrel, initially surging more than $7, as the nuclear alert and bank payment constraints heightened fears that oil shipments from the world's second-largest producer could be disrupted. Russia accounts for about 10% of global oil supply.
At 0228 GMT Brent crude futures were up $3.95, or 4%, at $101.88, after hitting a high of $105.07 a barrel in early trade. Last week the benchmark hit a more than seven-year high of $105.79 after Russia's invasion of Ukraine began.
The April Brent contract expires on Monday.