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RIYADH, Saudi Arabia — Saudi Arabia has mobilized 150,000 troops and some 100 fighter jets to rout Iran-linked fighters that have taken over swathes of neighboring Yemen, a security adviser to the kingdom told NBC News on Thursday.

The adviser, who asked that his name not be used, did not say whether any of Saudi troops had crossed the border into Yemen as part of the kingdom's military intervention to arrest Yemen's rapidly deteriorating crisis. But he said Saudi Arabia was in “complete control” of Yemeni airspace after launching airstrikes overnight and started implementing a no-fly zone.

The conflict risks becoming a proxy war between Sunni Muslim states and Shiite Iran, which Saudi Arabia accuses of supporting the Houthi rebels and trying to increase its influence throughout the region.

Iran quickly condemned the airstrikes launched by Saudi Arabia and its allies as "very dangerous."

"Many innocent people were killed,” Iran's Foreign Ministry spokeswoman Marziyeh Afgam said in a statement. “Regional governments should show respect to each other and peacefully resolve matters.”

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Iran's Foreign Minister Javad Zarif, who was in Switzerland for nuclear talks, said there was an “urgent need for dialogue” among Yemenis without “external interference.”

A broad-based coalition of nations — including the United Arab Emirates, Bahrain, Kuwait, Jordan, Morocco, Sudan and Qatar — were lending air support to the Saudi intervention with 115 additional fighter planes, the adviser said. Egypt and Pakistan were part of the broader coalition, he added.

Secretary of State John Kerry commended the work of the coalition and underlined U.S. support for the effort — including intelligence sharing, targeting assistance, and advisory and logistical help — in talks with his counterparts in the region on Thursday, a senior U.S. official said.

The escalation comes after Iran-linked Houthi rebels captured al-Anad airbase near the port city of Aden earlier in the week — an installation formerly used the U.S. and Europe in the fight against al Qaeda — as part of their power grab in the poor Arab nation.

While reports swirled that President Abed Rabbo Mansour Hadi, a close U.S. ally, had fled the country, those claims were denied by his nephew and key adviser Mohammed Hadi.

Saudi Arabia said strikes had destroyed compounds and military installations used by the Houthis and forces loyal to their ally, former President Ali Abdullah Saleh. Airstrikes were reported deep inside Yemen, including in capital Sanaa where homes near the international airport were flattened, according to The Associated Press.

An employee of the five-star Mercure hotel in the key port city of Aden told NBC News that he was hearing firing all around the building and called the situation a “mess.”

"We don't know who is in control,” said the worker who asked that his name not be used.

IN-DEPTH

— Lubna Hussain, F. Brinley Bruton, Alexander Smith and Charlene Gubash

Reuters and The Associated Press contributed to this report.