Here's a detailed report expanding on the incident, drawing from the provided details, official statements, expert commentary, and broader geopolitical context. I've structured it into short paragraphs for readability, using British English throughout.

A US submarine has sunk the Iranian frigate IRIS Dena off the coast of Sri Lanka, killing at least 87 Iranian sailors and sparking a fierce diplomatic storm. The warship had just participated in India's Milan naval exercise as a guest of the Indian Navy. Defence Minister Rajnath Singh addressed the crisis on Friday, emphasising India's duty as a maritime power without directly referencing the sunken vessel.

Speaking at the "Sagar Sankalp – Reclaiming India’s Maritime Glory" event in Kolkata, Singh declared that turmoil in West Asia underscores the oceans' strategic weight. "

As a major maritime nation, it is India's responsibility to provide leadership with confidence, capability, and a clear vision," he stated. The remarks came two days after the attack, which has escalated US-Iran tensions into India's regional backyard.

Iranian Foreign Minister Abbas Araghchi condemned the strike, noting that IRIS Dena was a "guest of the Indian Navy" in a non-combat posture. He described the assault as unprovoked, occurring without warning shortly after the frigate left Indian waters. Tehran has vowed retaliation, heightening fears of broader conflict in the Indian Ocean.

The Indian Navy responded swiftly to a distress call from the vessel, launching search and rescue operations in international waters off Sri Lanka. However, no ammunition was aboard the frigate per exercise protocols, leaving it defenceless, according to former Foreign Secretary Kanwal Sibal. Sibal highlighted India's role as host, arguing the US ignored New Delhi's sensitivities.

Sibal, writing on X (formerly Twitter), questioned the premeditation of the attack. He noted the US Navy's last-minute withdrawal from the Milan exercise, to which it had been invited. "The Iranian ship will not be where it was if we had not invited it," Sibal wrote, urging India to issue condolences on moral and human grounds.

Strategic analyst Brahma Chellaney raised alarms over potential intelligence sharing. He queried whether data from India-US pacts like COMCASA and LEMOA enabled the US submarine to track and target the frigate. Such an outcome, he argued, would breach the defence partnership's foundations, especially post-exercise.

Government sources dismissed these claims as "baseless and preposterous," per PTI reports. India has rejected allegations that its Navy shared intelligence with the US. The denial underscores New Delhi's delicate balancing act between its strategic ties with Washington and longstanding relations with Tehran.

International media has amplified the controversy. Bloomberg's headline read: "US Sinking of Iranian Warship Piles Pressure on India's Modi." Al Jazeera claimed the incident "blew a hole in Modi’s ‘guardian’ claims," referencing Prime Minister Narendra Modi's portrayal of the Indian Navy as protector of the Indian Ocean during Diwali 2024 aboard INS Vikrant.

Opposition parties in India have lambasted the Modi government, accusing it of prioritising US alignment over Iran ties. Critics argue the episode dents India's image as a neutral maritime leader. Yet, Modi himself has stayed silent on specifics, reiterating on Friday India's push for peace in Ukraine and West Asia.

The Milan exercise, hosted by India, featured multinational participation to foster maritime cooperation. IRIS Dena's crew had paraded before President Droupadi Murmu, symbolising goodwill. The US pull-out, now scrutinised, fuels speculation of ulterior motives tied to the submarine operation.

Broader implications loom for Indian Ocean security. The attack marks a rare extra-Gulf escalation between the US and Iran, near vital sea lanes for India's energy imports. Analysts warn it could disrupt trade routes and invite proxy responses, testing New Delhi's SAGAR (Security and Growth for All in the Region) doctrine.

Rajnath Singh's speech reframed the crisis as a call for Indian leadership. By avoiding direct comment on IRIS Dena, he sidestepped entanglement while asserting naval prowess. India's carrier Vikrant and growing blue-water capabilities position it to mediate, but trust erosion could complicate this.

Former diplomats like Sibal stress ethical duties. A simple condolence from the Navy, post-political clearance, could salve wounds without alienating allies. Silence risks perceptions of complicity, especially amid shared intelligence frameworks.

Geopolitically, the incident strains the Quad's anti-China focus, as US actions spotlight Iran tensions. India, importing 85% of its oil via these waters, cannot afford instability. Beijing has offered muted support to Tehran, potentially exploiting divisions.

As investigations continue, questions persist on the submarine's identity and rules of engagement. The US has not commented officially, but the strike's precision suggests advanced tracking—real or alleged. India's response will shape its maritime credibility.

The IRIS Dena sinking exposes fault lines in India's neighbourhood. Rajnath Singh's vision of confident leadership arrives at a pivotal moment, demanding deft diplomacy to reclaim maritime glory amid escalating powers.

Agencies