US State Department spokesman Matthew Miller told a news conference: "The Houthis' seizure of the Galaxy Leader in the Red Sea is a flagrant violation of international law."
"We demand the immediate release of the ship and its crew and will consult with our allies and partners at the United Nations on appropriate next steps."
Israel has confirmed that the Houthi group seized a cargo ship, which it said was owned by Britain and operated by Japanese, in the southern Red Sea, describing the incident as an "Iranian terrorist act" that will have repercussions on international maritime security.
"There were no Israelis on board," Netanyahu's office added, explaining that Israel does not share its ownership or operation.
"This is a new Iranian terrorist act that represents an escalation in Tehran's aggression against the citizens of the free world, and has international repercussions on the security of global shipping routes," he said. Iran has denied any involvement in the operation.
Israeli officials say the ship is British-owned and operated by Japan. However, the AP reported that ownership details in public shipping databases linked ownership of the ship to Ray Car Carriers, founded by Abraham "Rami" Ungar, known as one of Israel's richest men.
According to UK government data, a company called Ray Car Carriers was registered in London in 2010, but dissolved in May 2017 and was registered as Dan-David Ungar.
According to Reuters, the ship is owned by an Isle of Man-based company called Ray Car Carriers, a unit of Tel Aviv-registered Ray Shipping, which Israel denies.
The data also showed that the ship's automatic identification system (AIS) tracker was turned off after its hijacking.
A spokesman for Japan's Nippon Yusin Corp., also known as NYK, which operates the vessel, confirmed that a car-carrying ship had been seized in the Red Sea and that the company was gathering more information.
Japan's Nikkei newspaper reported that the ship's crew included 22 people, including Bulgarians and Filipinos. It noted that there were no Japanese nationals.
For its part, the Japanese government condemned the kidnapping and confirmed that it is seeking the release of the ship's crew.
Chief Cabinet Secretary Hirokazu Matsuno confirmed the seizure of the ship, adding that Japan was appealing to the Houthis to release the ship and asking for the help of the Saudi, Omani and Iranian authorities to work for the speedy release of the ship and its crew.
"We strongly condemn such acts," he told a news conference. There are no Japanese among the crew, he said.