Four were in the Gulf of Oman and one near Kharg Island, CENTCOM said.
President Donald Trump announced "major combat operations" against Iran on Feb. 28, with massive joint U.S.-Israeli strikes targeting military, government and infrastructure sites.
Delegations from the U.S. and Iran entered negotiations in June aimed at a war-ending deal based on a memorandum of understanding signed by both countries.
The U.S. and Iran have nonetheless continued to exchange strikes, with the strategic Strait of Hormuz as the primary flashpoint. Trump said in August that the U.S. would launch a "crushing economic operation" to force Tehran into submission.
An additional 30 troops have been wounded in the war with Iran, according to the Pentagon's casualty database.
As of Tuesday, 820 U.S. troops have been wounded and 18 have been killed.
-ABC News' Steve Beynon
Iran's Islamic Revolutionary Guard Corps issued a warning that all oil tankers in Kuwaiti and Bahrani waters be evacuated after an alleged U.S. attack on an Iranian oil tanker.
"In light of the atrocities committed by the terrorist US army in targeting several tankers of the Islamic Republic of Iran, we warn all tanker crews in the Kuwaiti and Bahraini ports, which host these terrorists and are partners in their atrocities, to immediately abandon their vessels, whether at anchor or at the ports, because they will be targeted," Iran's IRGC Navy said in a statement Tuesday.
Iran state media claimed the U.S. attacked an oil tanker near Kharg Island on Tuesday.
According to a report from Tasnim News Agency, a small Iranian oil tanker, located 4 nautical miles from Kharg Island, was the target of a missile attack by the U.S. military.
The tanker was struck by a projectile fired by U.S. forces in the vicinity of Kharg Island's anchorage, Tasnim said.
Tasnim said there are no reported casualties.
-ABC News' Desiree Adib
Iran claimed it seized an American underwater drone that the U.S. said had malfunctioned.
An underwater drone operated by the U.S. malfunctioned “more than a day ago” when it was surveying waters in the Middle East, a U.S. official told ABC News.
The same U.S. official said that the drone was "an older model that neither collected sensitive data nor carried any classified sonar or radar equipment."
