The United States carried out a cyberattack earlier this month against two Iranian military ships as part of its multipronged response to the killing of three U.S. soldiers by Iran-backed proxies, VOA has confirmed.

A U.S. official, who spoke to VOA on the condition of anonymity because of operational sensitivities, said the MV Behshad was one of the targeted ships The Iranian military ship was collecting intelligence on vessels in the Red Sea and the Gulf of Aden. A source with knowledge of the cyberattack said an Iranian frigate was also targeted.

The U.S. official said the cyberattack on the MV Behshad was to inhibit its ability to share targeting information with the Iranian-backed Houthi rebels in Yemen who have been firing missiles into international shipping lanes.

Earlier this month, White House national security adviser Jake Sullivan warned of potential “unseen” retaliatory efforts “to send a very clear message that when American forces are attacked, when Americans are killed, we will respond, and we will respond forcefully.”

Pentagon press secretary Major General Pat Ryder declined to comment to VOA about the attack, which an official said occurred more than a week ago.

NBC News first reported the attack on the Iranian spy ship on Thursday but did not report the cyberattack on the Iranian frigate.

U.S. officials do not typically disclose covert operations, including cyberattacks.

In addition to the cyberattacks, the U.S. this month struck Iranian-backed proxies in seven locations across Syria and Iraq on February 2.

A day later, U.S. and allied forces struck dozens of Houthi targets at 13 locations in militant-controlled areas of Yemen.

A U.S. drone strike on February 7 in Baghdad killed a Kataib Hezbollah commander who the U.S. said was “responsible for directly planning and participating in attacks on U.S. forces in the region.”

There has not been an attack on U.S. troops in Iraq, Syria or Jordan since February 4, according to the Pentagon.

U.S. troops in Iraq, Syria and Jordan were attacked by Iran-backed militants more than 160 times since mid-October, shortly after Hamas’ assault on Israel. Most of the attacks caused few to no injuries or damages, but an attack in late January at the Tower 22 base in Jordan killed three American service members and wounded dozens of others.

Iranian-backed Houthi militants, however, have continued with their series of attacks targeting international shipping lanes in the Red Sea and the Gulf of Aden.

The Houthis say the attacks are in solidarity with Palestinians in the Gaza Strip. According to a U.S. defense official, the Houthis have attacked or threatened commercial vessels 48 times since mid-November.

The U.S. has carried out self-defense strikes against Houthi drones and missiles that have been fired into international shipping lanes or that were poised to conduct attacks. The U.S. and its partners also carried out attacks in Houthi-controlled areas of Yemen last month, which they said took out key weapons used in the Houthis’ targeting of international ships.