The airstrikes came after Iran-backed rebel groups marched on the port city of Aden

Oil prices rose by almost 6% after Saudi Arabia, the world's biggest crude exporter, and its allieslaunched airstrikes on rebel targets in Yemen.

The move has raised concerns that the conflict could spread in the oil-rich Middle East and possibly disrupt supplies from the region.

West Texas Intermediate crude futures, the US benchmark, rallied to about $51 (£34) a barrel before falling back.

Brent crude climbed to $59.71 a barrel, but has since dipped to $56.50.

Pressure on the oil price eased slightly as it became clear there was no immediate threat to Middle East oil shipments. However, fears remain that Iran could be drawn into the conflict.

Yemen is located along an important international shipping route for global energy producers. But the country is sliding towards civil war.

Houthi rebels receiving support from Iran have marched on the southern Yemeni port city of Aden, where Yemen's President Abdrabbuh Mansour Hadi took refuge after he was forced him to flee the capital, Sanaa.

Saudi Arabia, supported by regional allies the United Arab Emirates, Bahrain, Qatar and Kuwait, launched airstrikes on Thursday aimed at halting the rebel advance.

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