A Japanese tanker loaded with chemicals was hit by a drone off India "fired by Iran", the Pentagon said in a sign of increasing risk to commercial traffic outside the Red Sea, AFP reported.

It is the first time the Pentagon has openly accused Iran of directly striking ships since Israel's war against the Tehran-backed radical Hamas movement began on October 7.

The attack comes amid drone and missile attacks by Yemen's Houthi rebels, also backed by Iran, in a key shipping area in the Red Sea. The Houthis say they are attacking in solidarity with Hamas and the Palestinians in the Gaza Strip.

Saturday's attack in the Indian Ocean took place around 10 a.m. local time and did not cause casualties on board the ship, a fire broke out that was extinguished, the Pentagon said.

The US military "remains in communication with the ship, which is proceeding to its destination in India".

The drone strike took place about 200 nautical miles (370 km) off the Indian coast.

The Pentagon announced that the Chem Pluto tanker, sailing under the Liberian flag and managed by a Dutch company, is owned by a Japanese company. According to the Wall Street Journal, the Dutch company is linked to an Israeli businessman.

Separately, a US warship shot down four drones fired from Houthi-held areas in Yemen on Saturday, the Pentagon's Central Command said. There were no injuries or damage.