The collapse of the American-backed government in Yemen took the U.S. intelligence community by surprise, the Obama administration's senior counterterrorism official admitted on Thursday as he testified before Congress, according to The Associated Press.

Nicholas Rasmussen told the Senate intelligence committee Yemen's army failed to oppose advancing Shiite militants known as Houthis who in September entered the country's capital, Sanaa, and last month ousted President Abed Rabbo Mansour Hadi.

The director of the National Counterterrorism Center compared the situation to the effective refusal of the Iraqi military to fight Islamic State militants last year. Both the Yemeni and the Iraqi armed forces had been backed by the United States.

What happened in Iraq occurred in Yemen on "a somewhat smaller scale," Rasmussen noted.

"As the Houthi advances toward Sanaa took place ... they weren't opposed in many places," he said. "The situation deteriorated far more rapidly than we expected."

Missouri Sen. Roy Blunt, a Republican member of the intelligence committee, aggressively questioned Rasmussen and noted President Barack Obama recently touted Yemen as a success story.

Now, it's a "total disaster," Blunt said.

Rasmussen admitted the the collapse of the government and this week's evacuation of the U.S. Embassy in Sanaa complicate efforts to contain the Yemeni arm of al-Qaida, considered one of the terror group's most dangerous branches.

The organization appeared to be taking advantage of the turmoil by overrunning a military base in southern Yemen on Thursday, the Washington Post noted. Militants linked to al-Qaida mounted a sophisticated attack in which six soldiers were killed and three more wounded.

Before his ouster, Hadi had supported a U.S. drone program that targets the Yemeni group, which refers to itself as al-Qaida in the Arabian Peninsula.

During his testimony, Rasmussen, meanwhile, also commented on other flashpoints of violence in the Middle East. He acknowledged that ISIS, the Islamic terror organization that controls large swaths of territory in Syria in Iraq, is now also considered the dominant extremist group in the Libyan cities of Derna and Benghazi.

Militants in Afghanistan, Egypt and Algeria had also pledged their allegiance to ISIS, which calls itself the "Islamic State." In his view, the development signals the group's increasing predominance over its rival, al-Qaida, Rasmussen told the panel.