New US sanctions that will hit Iran’s energy industry and the fallout of Venezuela’s economic collapse have raised fears of tighter global oil supplies, sending prices above $80 a barrel for the first time in nearly four years.

Brent crude had been rising even before President Donald Trump announced the US withdrawal from the nuclear deal and reimposed restrictions on Iranian oil exports this month, with prices climbing more than 40 per cent over the past year.

But the prospect of fewer barrels from Iran and Venezuela has sent Brent, the international benchmark, up more than $5 a barrel in May alone. Those pressures, on top of agreed output cuts by Opec and Russia and robust oil consumption spurred by a healthier global economy, has convinced some investors that prices could head even higher.