Indian Foreign Minister Subrahmanyam Jaishankar has called US Secretary of State Marco Rubio in protest after American strikes on three largely Indian-crewed merchant vessels off Oman killed three Indians, upping the diplomatic ante.

The call came after New Delhi summoned a senior US diplomat in the Indian capital for a second time in two days over the incident.

"Spoke to US Secretary of State Marco Rubio this evening," Jaishankar said early Saturday in a post on X.

"I reiterated India's strong protest at the attacks by the US Navy in the Gulf that killed three Indian mariners. Such lethal actions against commercial shipping are not justified."

On Wednesday, three Indian sailors were killed in a US strike on the Palau-flagged MT Settebello off the coast of Oman.

That followed a June 8 strike on the MT Marivex, another Palau-flagged tanker. Omani authorities airlifted 24 Indian sailors off the stricken vessel.

On Thursday, a Guinea-Bissau-flagged tanker was hit in a US strike. New Delhi said its crew, who included 20 Indian sailors, were rescued.

US Deputy Chief of Mission Jason Meeks was summoned twice in New Delhi to hear India's protest, Jaishankar's ministry said.

The US State Department did not immediately comment on the call between Jaishankar and Rubio, but had earlier said it was in "direct contact" with the Indian government on the issue.

India is one of the largest contributors of sailors on merchant shipping worldwide, with more than 320,000 active seafarers in 2025, according to the country's shipping ministry.

That ministry warned on Thursday all Indian sailors "serving onboard Indian and foreign-flagged vessels transiting through conflict-affected waters to exercise the highest degree of caution".

India's navy also said Thursday that it had carried out a "high-risk operation" to extract an unexploded missile warhead from the crude oil tanker MT Olympic Life.

The Marshall Islands-flagged tanker was struck off the coast of Oman on May 26, but safely limped to India's southern port of Kochi.

India's navy said that the "projectile had penetrated the vessel's hull, traversed multiple structural compartments and was lodged inside a fuel tank".

Iran has restricted shipping through the Strait of Hormuz -- which normally carries about one-fifth of the world's oil and liquefied natural gas shipments -- since the United States and Israel launched attacks on February 28.

The United States has imposed its own naval blockade on Iranian ports.