In back and forth attacks, the US hit five Iranian tankers in reprisal strikes after Tehran targeted one of its warships. Brent crude - which is the global benchmark for prices - has not been as expensive since the end of July, when a ceasefire between Iran and the US collapsed. Yemen's Iran-backed Houthi movement also attacked oil facilities in Saudi Arabia on Tuesday and have been targeting tankers in the Red Sea. Brent crude did dip back down to $99.90 a barrel, but any fresh flare-ups in the Middle East could see it pushed higher again. Tit-for-tat strikes between Iran and the US have escalated in the past week, more than six months after conflict broke out when the US and Israel launched attacks on Iran on 28 February. Oil prices have fluctuated wildly since the war began, and pressure on the industry has been exacerbated by wider regional instability. Before the conflict Brent crude had been priced at about $70 (£52) a barrel. But the war has seen the effective closure of the Strait of Hormuz, which carries 20% of the world's oil and liquefied natural gas (LNG). The rising costs have sparked huge price leaps in petrol around the world for motorists at the pumps. The US strikes on the five Iranian tankers saw four in the Gulf of Oman linked to Iran's Revolutionary Guards Corps (IRGC) hit as well as another near Kharg Island. Tehran responded by launching missiles at a US base in Jordan - most of which were shot down - and said it attacked two US vessels and eight oil tankers in the Strait of Hormuz. The Houthis and Saudi Arabia have also been exchanging strikes since July after their own informal ceasefire unravelled. On Monday the Houthis accused Saudi Arabia of bombing a prison in al-Hazm and killing 11 people. (BBC)