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A Japanese-owned chemical tanker struck Saturday off the coast of India was targeted by a drone "fired from Iran," the Pentagon said, a sign of expanding risks to commercial shipping beyond the Red Sea.

It was the first time the Pentagon has openly accused Iran of directly targeting ships since the start of Israel's war on the Palestinian group Hamas, which is backed by Tehran.

The attack came amid a flurry of new drone and missile attacks by Yemen's Iran-backed Houthi rebels on the vital Red Sea shipping lane since the start of the Israel-Hamas war on October 7, with the group claiming to act in solidarity with Gaza.

Saturday's Indian Ocean attack took place around 10 am local time (0600 GMT) and caused no casualties aboard the vessel, a Pentagon statement said, adding that a fire was extinguished.

The US military "remains in communication with the vessel as it continues toward a destination in India," it added.

The drone strike occurred 200 nautical miles (370 kilometres) off the coast of India, it said, adding that no US Navy vessels were in the vicinity.

The Pentagon statement said the MV Chem Pluto ship flew under a Liberian flag and was operated by a Dutch entity, although the ship is owned by a Japanese company.

Ambrey, a maritime security firm, said the "chemical/products tanker... was Israel-affiliated" and had been on its way from Saudi Arabia to India.

The Wall Street Journal reported that the Dutch company operating the MV Chem Pluto "is connected to Israeli shipping tycoon Idan Ofer."

The Indian navy said it had responded to a request for assistance.

"An aircraft was dispatched and it reached overhead the vessel and established safety of the involved ship and its crew," a navy official told the media.

"An Indian navy warship has also been dispatched so as to provide assistance as required."

There was no immediate claim of responsibility for the strike.

Agence France-Presse