Yemen’s Iran-aligned Houthi group said it attacked two plants at the heart of Saudi Arabia’s oil industry on Saturday, knocking out more than half the Kingdom’s output, in a move expected to send oil prices soaring and increase tensions in the Middle East.

The attacks will cut the kingdom’s output by 5.7 million barrels per day (bpd), according to a statement from state-run oil company Saudi Aramco, or more than five percent of global oil supply.