The country’s exports mostly come from Kharg Island in the Persian Gulf. But Israel’s energy facilities are also at risk.

The Iran shock presents two risks to the price of oil, which rose 8 per cent to $74 a barrel on Friday morning, a sizeable jump for a single day. The first is that, in the context of the rising hostilities, Iran’s current crude exports, which have already been softening, could fall further.

Fears that Israel may destroy Iranian oil facilities to deprive it of its main source of revenue have driven oil prices higher.

Crude futures jumped more than $5 a barrel on Friday after Israel launched airstrikes against Iran without U.S. support.

Iran has in the past threatened to disrupt shipping through the Strait of Hormuz if it is attacked. The Strait is the exit route from the Middle East Gulf for around 20% of the world's oil supply, including Saudi, UAE, Kuwaiti, Iraqi and Iranian exports.

Iran has partially suspended gas production at the world's biggest gas field after an Israeli strike caused a fire there on Saturday, the semi-official Tasnim news agency reported, in what would be the first Israeli strike on Iran's oil and gas sector.

Market watchers believe a full-scale disruption of global oil flows by closing the waterway is unlikely, and might even be physically impossible.

NEW YORK (Reuters) -Dual risks kept investors on edge ahead of markets reopening late on Sunday, from heightened prospects of a broad Middle East war to U.S.-wide protests against U.S. President Donald Trump that threatened more domestic chaos.