South Korea’s Hanwha Group says it is a “credible buyer” and has made a “highly competitive” offer for Austal despite the ASX-listed naval shipbuilder rejecting a $1 billion takeover proposal from the defence and aerospace conglomerate.

Austal told investors it had declined to give Hanwha access to non-public information for due diligence because it was “not satisfied” that the bid would secure the necessary approvals from defence agencies in Australia and the United States.