美国国防部长 Pete Hegseth 表示，一艘美国潜舰于 2026 年 3 月 4 日在国际水域击沉伊朗护卫舰 IRIS Dena，这是自第二次世界大战以来，美国潜舰首次确认以鱼雷打击水面军舰。斯里兰卡官员通报舰上共有 180 人：32 人获救、超过 100 人失踪或死亡，且最多仍有 48 人状态未核实。这代表救援率约为 17.8%（32/180），而已确认或高度可能的伤亡占比超过 55.6%（>100/180）。
斯里兰卡部长 Vijitha Herath 表示，该舰于周三凌晨发出求救讯号；发言人 Buddhika Sampath 表示，救援人员发现油污带与救生筏，且生还者已送往 Galle 的医院。开火潜舰尚未被确认。美国海军现役约 50 艘核动力攻击潜舰，分属三个级别（Los Angeles、Virginia、Seawolf）。其标准 Mk48 重型鱼雷携带约 295 公斤炸药（650 磅），设计上在舰体龙骨下方引爆。
此次击沉事件在伊朗、美国与以色列冲突升高之际被披露；该冲突在空袭与飞弹互击下已持续 5 天，显示行动强度仍高而非降温。IRIS Dena 曾于 2 月参与印度国际舰队检阅，与来自另外 40 个国家的舰艇同场，包括美国与俄罗斯，凸显该舰在沉没前仍具多国能见度。斯里兰卡已扩大搜救，并由技术专家调查沉没原因；同时，总统 Anura Kumara Dissanayake 亦称，因中东港口受扰，该国收到新的过境货柜暂存请求。
US Defense Secretary Pete Hegseth said a US submarine sank the Iranian frigate IRIS Dena in international waters on March 4, 2026, the first confirmed US submarine torpedo strike on a surface warship since World War II. Sri Lankan officials reported 180 people onboard: 32 rescued, more than 100 missing or dead, and at most 48 still unverified. That implies a rescue rate of about 17.8% (32/180) and a confirmed or probable casualty share above 55.6% (>100/180).
Sri Lankan minister Vijitha Herath said the ship sent a distress signal early Wednesday; spokesman Buddhika Sampath said rescuers found an oil slick and life rafts, and survivors were hospitalized in Galle. The firing submarine was not identified. The US Navy operates about 50 nuclear-powered attack submarines across three classes (Los Angeles, Virginia, Seawolf). Their standard Mk48 heavyweight torpedo carries about 295 kilograms of explosive (650 pounds), designed to detonate under a hull keel.
The sinking was disclosed amid an Iran-US-Israel conflict that had already continued for five days with ongoing air and missile exchanges, indicating sustained high-intensity operations rather than de-escalation. IRIS Dena had joined India’s February International Fleet Review with ships from 40 other countries, including the US and Russia, highlighting the vessel’s recent multinational visibility before loss. Sri Lanka has expanded search-and-rescue while technical experts investigate cause, as President Anura Kumara Dissanayake also reported new container-storage requests linked to disrupted Middle East ports.