Houthi rebels in Yemen have hijacked a British-owned cargo ship in the Red Sea that's operated by a Japanese company. The militant group claims the vessel belongs to Israel.

Houthi spokesperson Yahya Sarea said in a video statement, "We reiterate our warning to all ships affiliated with the Israeli enemy or those working with it. They will all become legitimate targets of our forces."

The spokesperson warned that the group will continue to carry out operations against Israel until the offensive in the Gaza Strip stops.

The seized cargo ship, Galaxy Leader, is operated by Nippon Yusen, also known as NYK Line.

Israel says the ship isn't theirs -- and none of its nationals are on board.

But according to major Israeli media outlets such as Haaretz, the ship is owned by a company affiliated with a wealthy business person from Israel.

Hamas praised the Houthi seizure, saying it was a welcome step.

The cargo ship was traveling from Turkey to India via the Red Sea, when it reportedly lost contact in the waters off the coast of Saudi Arabia on Saturday night. It's used to transport cars by sea -- but had no cargo when it was seized.

A Japanese expert on the Middle East and a Professor of Keio University, Tanaka Koichiro, says the Houthis had their own reasons for targeting the ship.

Tanaka says it's possible that the parent company has Israeli capital, and the rebels did their research and knew that when they decided to target this ship.

He added the ship could be used in negotiations as a bargaining chip.

The Houthis are based in Yemen and have grown with Iran's support. They're believed to have about 20,000 armed fighters, as well as ballistic missiles.

The group has been repeatedly firing those missiles into Israel since the current conflict began. It has also fired unmanned aircraft towards the country.

The Houthis have reportedly stepped up activities in the Red Sea recently, threatening safe navigation in the area.

Japan's Coast Guard issued warnings to all Japanese ships in the Red Sea after the seizure. Japan's defense officials say they are now collecting more information about the incident.