New Aukus drone subs to protect critical undersea cables as Marles warns: ‘seabed is a battlefield’

Minister at Singapore defence summit also reveals Australia to buy only secondhand Aukus submarines from US

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The defence minister, Richard Marles, has said the “seabed is a battlefield” in a combative speech urging Beijing to be more transparent about its maritime operations, and taking aim at weak international controls over so-called “shadow-fleet” 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.