The US military carried out a "precision" strike on a vessel in the Gulf of Oman that failed to follow its instructions and was carrying oil from Iran, it said, while India said three Indian seafarers were missing after the attack on the tanker.
The US began a blockade of Iran-related shipping on April 13 after Iran severely curtailed shipping through the Strait of Hormuz, a major global oil and gas route.
The US military's Central Command (Centcom) said a US aircraft, "fired precision munitions into the ship’s engine room after the crew repeatedly failed to comply with directions from American forces".
Centcom said on Wednesday it disabled the Palau-flagged oil products tanker Settebello as it transited the Gulf of Oman, adding that it had, "violated the ongoing blockade by attempting to transport oil from Iran".
India summoned the US deputy chief of mission to the country after lodging a "strong protest" to the strike, two Indian sources with direct knowledge of the matter told Reuters on Wednesday.
India's foreign ministry earlier on Wednesday condemned what it said was an, "attack on the commercial vessel Settebello".
"Our embassy in Oman is closely monitoring the situation and proactively co-ordinating with the Omani authorities in the ongoing search and rescue operation," the ministry said in a statement, adding 21 Indian mariners had been rescued.
"The targeting of commercial shipping and civilian infrastructure in the region must end," it added.
The ship was a chemical/oil products tanker which reported an engine room fire 20 nautical miles northeast of Oman's port of Sohar, the United Kingdom Maritime Trade Operations agency said.
Earlier, UKMTO had said that the vessel's crew had reported one casualty, without giving further details. It was unclear if the casualty was among the rescued or the three missing.
The vessel's India-based operator, listed in databases, could not be reached for comment.
The Omani Navy responded to the Settebello distress call, British maritime risk management group Vanguard said.
The tanker was partially laden and last located off Oman's coast on June 1, according to the MarineTraffic ship-tracking platform.
Centcom said on Wednesday its forces had disabled eight non-compliant vessels, redirected 134 ships that complied, and allowed 42 vessels supporting humanitarian aid to pass since initiating the blockade on April 13.
There have been no reports of fatalities stemming from these operations.
US forces disabled the unladen Marivex oil tanker in the Gulf of Oman on Monday after it attempted to sail to an Iranian port in violation of the ongoing blockade against Iran, the US military said.
Ships being targeted include Iranian vessels as well as so-called shadow fleet tankers, which are typically older vessels without Western insurance used to transport sanctioned oil and sailing under the flags of various nations to obscure their true ownership, cargo and movements.
"I strongly condemn any act from any party that endangers the lives of seafarers and the safety of international shipping. This is simply unacceptable," Arsenio Dominguez, secretary-general of the UN's shipping agency the International Maritime Organisation, said on Wednesday after the incident.
"My thoughts are with the families of the three missing seafarers and with all those awaiting news of the crew members."
(Reporting by Jonathan Saul, Nidhi Verma, Aftab Ahmed, Saurabh Sharma and Ahmed Elimam; editing by Alex Richardson, Jason Neely, Alexandra Hudson)