SANAA, Yemen — A group of Gulf countries denounced the Shiite rebel takeover of Yemen as a "coup" Saturday, calling for the United Nations to take action as thousands demonstrated in the streets against their power grab.

The rebels, known as Houthis, have taken over state institutions, dissolved parliament and installed a new committee to govern the Mideast's poorest country — which is also home to what Washington considers al-Qaida's most dangerous franchise.

The six Arab countries of the Gulf Cooperation Council, led by Sunni-ruled Saudi Arabia and the United Arab Emirates, issued a statement Saturday carried by the official Saudi Press Agency calling for the U.N. Security Council to "put an end to this coup."

"The Cooperation Council sees Houthi coup as an escalation that cannot be accepted under any circumstances," the council said.

The council serves as a counterbalance to regional Shiite power Iran, which the council previously has accused of meddling in their internal affairs. Critical described Iran as a key backer of the Houthis, something the rebels deny.

In a defiant speech Saturday, rebel leader Abdel-Malak al-Houthi said his group's takeover of the government was necessary.

"The constitutional declaration ... came to end the vacuum," he said. "It's all in the interest of the people, and for the people, and for facing these threats and conspiracies against the people."

However, the vacuum came after former President Abed Rabbo Mansour Hadi and his government resigned after Houthi rebels besieged them in the capital, Sanaa.

In its first decree, the Houthi committee appointed Mahmoud al-Subeihi as Yemen's acting defense minister and Jalal al-Rowaishan as acting interior minister. The two held the positions in the former government but resigned along with Hadi last month.

An official close to al-Subeihi said the two ministers were being "forced" to return to their posts. He spoke on condition of anonymity because he wasn't authorized to speak to journalists

On Saturday, thousands protested in Sanaa, as well as the cities of Hodeida, Ibb and Taiz. Meanwhile, thousands rallied in support of the Houthis at a sports stadium in Sanaa.