The front month contract on Brent crude, the international standard for oil prices, crossed $100 per barrel again on Wednesday morning while the US standard, WTI, hovered around $95.
Prices have risen almost 20% since the middle of last week as fighting around the world's most important oil chokepoint has once again intensified.
It is also the first time since 23 July that oil has hit the $100 mark.
US Central Command said its forces destroyed five Iranian tankers carrying crude oil on 8 September after Iran's Revolutionary Guard fired ballistic missiles at a US Navy warship twice within two days. The command did not identify the ship, but said it was not hit and continued patrolling regional waters.
It followed a similar strike on 5 September, when Iranian forces fired ballistic missiles at a US aircraft carrier and a destroyer, both of which evaded the attack. The command responded by disabling or destroying three Iranian tankers.
