The U.S. has yet to determine who was responsible for the launch of missiles at Navy warships in the Red Sea from areas in Yemen in the control of Iranian-backed Houthi rebels, a Pentagon spokesman said Thursday.

"We don't know who was pulling the trigger," Pentagon Press Secretary Peter Cook said, but the missiles were launched from "Houthi-controlled territory in Yemen. Iran has played a role and been supportive of the Houthi rebels." The Houthis have denied carrying out the attacks.

At 4 a.m. local time Thursday, the Arleigh Burke-class destroyer USS Nitze launched missiles at three radar sites in coastal Yemen in retaliation for the attempted attacks on Navy warships, Cook said.

The initial assessment was that the sites were destroyed and there were no indications of civilian casualties, he added.

"These strikes were in response to attempted missile attacks in recent days against USS Mason and other vessels in the Red Sea and Bab-el-Mandeb," Cook said at a Pentagon news conference.

"We will be prepared to respond again" if ships in the Red Sea and the Bab-el-Mandeb Strait are threatened, Cook said. He declined to respond to reports that Iran has deployed two of its warships off Yemen in the Gulf of Aden. "I'll leave it to the Iranians to describe the disposition of their ships."

The Defense Department on Tuesday had warned of possible retaliation after a pair of missiles was fired at the Navy destroyer USS Mason on Sunday as the ship was in international waters near the Bab el-Mandeb Strait at the southern end of the Red Sea.

On Wednesday, another two missiles were fired at the Mason from an area believed to be in the control of the Houthis. None of the missiles struck the ship, and there were no injuries, U.S. officials said.

The amphibious transport dock ship USS San Antonio and the amphibious transport dock USS Ponce were also operating in the area with the Mason at the time.

The attempted attacks on U.S. ships were the first in the civil war between Shiite Houthi rebels fighting the government of President Abd Rabbuh Mansur Hadi that broke out in March 2015.

At least 4,125 civilians have been killed in the fighting, according to the United Nations High Commissioner for Human Rights. A cease-fire and peace talks collapsed in August.

Saudi Arabia, which backs the fledgling Yemeni government, began conducting airstrikes in Yemen last year.

A Houthi military official said that charges of missile launches by them at U.S. ships were an attempt at glossing over a Saudi airstrike on a funeral service Sunday that reportedly killed more than 150 people, the Houthi-affiliated Saba news agency reported.

White House Deputy Press Secretary Eric Schultz told reporters that the strikes on the radar sites "were indeed authorized by the president. These were ordered in response to the missile launches threatening the USS Mason."

"The intent of our strikes were to deter future attacks and to reduce the risk to U.S. and other vessels. We are prepared to respond if necessary to any future missile launches," Schultz said. He called the strikes a "purely self-defense action."

-- Richard Sisk can be reached at Richard.Sisk@Military.com.