Here's what we know so far about the incident:
All crew members, including around 20 Indians, are safe, officials said.
Merchant ship MV Chem Pluto, a Liberia-flagged oil tanker, set sail from a port in Saudi Arabia with crude oil.
It was headed for Mangalore when it was struck by a drone in the Arabian Sea 217 nautical miles off the Porbandar coast.
The attack caused a fire onboard, the officials said. As the vessel sent out an SOS for the fire, an Indian Coast Guard ship, ICGS Vikram, was moved towards the vessel, they said, adding that the fire was now extinguished but the vessel's functioning was affected.
ICGS Vikram was on patrol of the Indian Exclusive Economic Zone when it was directed towards the merchant ship in distress and alerted all ships in the area to extend assistance to the affected vessel.
Indian Coast Guard's Dornier maritime surveillance aircraft has established communication with the distressed vessel. The ship switched off its Automatic Identification System - used to track the vessel - after the attack.
"The power generation system of the ship is now functional and more checks are being carried out before it sets out for its destination," the Coast Guard officials said, reported news agency ANI.
The vessel has started moving at a speed of about 11 nautical miles an hour and will be joined by ICGS Vikram around 10 pm, Coast Guard officials said. It is expected to reach Mumbai by early December 25, they added.
According to the British military's United Kingdom Maritime Trade Operations, or UKMTO, "authorities were investigating" the incident, reported news agency AFP.
The incident comes days after the Indian Navy aided the evacuation of an injured sailor from a hijacked Malta-flagged cargo vessel on Monday. According to reports, six "pirates" had illegally boarded the ship, the MV Ruen, in the Arabian Sea.
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