People search for survivors under the rubble of houses destroyed by an air strike near Sanaa Airport March 26, 2015.[Photo/Agencies]

ADEN/WASHINGTON - Saudi Arabia and Gulf region allies launched military operations including air strikes in Yemen on Thursday, officials said, to counter Houthi fighters besieging the southern city of Aden where Yemeni president had taken refuge.

Gulf broadcaster al-Arabiya TV reported that the kingdom was contributing as many as 150,000 troops and 100 warplanes to the operations and that Egypt, Jordan, Sudan and Pakistan were ready to take part in a ground offensive in Yemen.

There was no immediate confirmation of those figures from Riyadh. Al-Arabiya also said planes from Egypt, Morocco, Jordan, Sudan, Kuwait, the United Arab Emirates, Qatar and Bahrain were taking part in the operation.

A widening Yemen conflict could pose risks for global oil supplies, and Brent crude oil prices shot up nearly 6 percent soon after the operation began.

Unidentified warplanes had earlier launched air strikes on the main airport in the Yemeni capital, Sanaa, and its al Dulaimi military airbase, residents said.

That came soon after Saudi Arabia's ambassador in Washington, Adel al-Jubeir, announced the operation.

"We will do whatever it takes in order to protect the legitimate government of Yemen from falling," Jubeir told a news conference.

Yemen's slide towards civil war has made it a crucial front in mostly Sunni Saudi Arabia's rivalry with Shi'ite Iran, which Riyadh accuses of stirring up sectarian strife throughout the region and in Yemen with its support for the Houthis.

The crisis now risks spiralling into a proxy war with Iran backing the Houthis, and Saudi Arabia and the other regional Sunni Muslim monarchies supporting Yemeni President Abd-Rabbu Mansour Hadi.

Fighting has spread across the Arabian peninsula country since last September, when the Houthis seized Sanaa and advanced into Sunni Muslim areas, forcing Hadi out of the capital.