India summoned the U.S. chargé d’affaires in New Delhi and delivered a formal protest following the deaths of three Indian sailors aboard an oil tanker allegedly attacked near the coast of Oman.

Official sources said it was the second such protest within a week, following a previous complaint regarding an attack on a commercial vessel.

India’s Minister of Maritime Affairs stated that the sailors were killed in the attack on a tanker sailing under the flag of Palau.