An Iranian warship destroyed in a US torpedo strike on Wednesday was "defenceless" and participating in an international naval exercise as a guest of the Indian navy, according to reports.

Former Indian Foreign Secretary Kanwal Sibal said “the Iranian ship will not be where it was if we had not invited it to talk [sic] part in our Milan exercise”. Sibal added that because it was taking part in an exercise “it was defenceless”.

Indian politician Supriya Shrinate said on social media: "These Iranian navy men parading at an event in India, were our guests. Invited by us.

"US submarine targeted their ship and killed them while they were returning home." Shrinate also criticised Indian Prime Minister Narendra Modi for his failure to make a statement on the attack.