Richard Marles speaks at the Shangri-La Dialogue in Singapore, which brings together defence officials from around the world. Photograph: How Hwee Young/EPA View image in fullscreen Richard Marles speaks at the Shangri-La Dialogue in Singapore, which brings together defence officials from around the world. Photograph: How Hwee Young/EPA New Aukus drone tech to protect critical undersea cables as Marles warns: βseabed is a battlefieldβ Minister at Singapore defence summit also reveals Australia to buy only secondhand Aukus submarines from US Follow our Australia news live blog for latest updates Get our breaking news email , free app or daily news podcast The defence minister, Richard Marles , has said the βseabed is a battlefieldβ in a combative speech urging Beijing to be more transparent about its maritime operations, and taking aim at weak international controls over so-called βshadow-fleetβ vessels. The warning came as the US, UK and Australia announced a new Aukus project to develop new underwater drone technology to protect undersea cables. The same announcement also revealed that Australia would buy three secondhand Virginia-class submarines from the US under Aukus, instead of a mix of old and new, in a move to βsimplify supply chain management, operational and maintenance requirements, and maximise cost efficienciesβ. As Aukus spending and delays blow out, will Australiaβs nuclear submarines ever materialise? Read more Speaking at the Shangri-La Dialogue in Singapore, Marles said undersea internet cables β βthe arteries of modern civilisationβ β were being cut at an unprecedented rate, with island nations like Australia acutely vulnerable. βThe seabed is becoming a battlefield. The shadow fleet is becoming a weapon,β he told Asiaβs largest defence summit. βOver the past 18 months, we have witnessed a series of attacks against subsea critical infrastructure at a scale and frequency that is historically unprecedented. βThis is not speculation. This is a documented pattern of behaviour. And we must reckon with it honestly.β Marles cited five cases of cables being cut in the Taiwan Strait in the past 18 months, attributed to China , and three in the Baltic Sea, alleged to have been committed by Russia. βNow, maybe these were accidents. But even if they were, it highlights the vulnerability of this crucial part of the globeβs infrastructure,β Marles said. βIf they were intentional, we are left to wonder: are countries testing our response times, testing our attribution thresholds and testing our political will to respond?β Sign up for the Breaking News Australia email The US secretary of defence, Pete Hegseth , announced the first βsignature projectβ for the second pillar of the Aukus treaty, whose first pillar is the nuclear submarine project. βThis signature project will deliver a suite of highly adaptable multi-mission UUV payloads designed to support undersea operations and maintain our collective advantage in the maritime domain,β he told