Oil prices recently rose sharply after the killing of a top Iranian general in Iraq.
Analysts warned the action could escalate tensions in the region and affect global oil production.
The price of Brent crude jumped by more than 3% and at one point hit $69.50 a barrel, the highest since September.
However, The global benchmark for crude oil rose above $70 a barrel on Monday for the first time in over three months, with jitters rising over the escalating military tensions between Iran and the United States.
All seven bourses in the Gulf Cooperation Council (GCC) states closed in the red, on the first trading day since the death of powerful military commander Qasem Soleimani.
All six member states — Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates are US allies and lie on the opposite side of the narrow Gulf, making them easy targets for the Islamic republic.