SYDNEY — Struggling upmarket Australian department store David Jones Friday received an unsolicited US$1.67 billion takeover offer from a British private equity firm. The retail giant, which is battling weak consumer sentiment and an explosion in online shopping, initially said it was unaware of the suitor but subsequently announced it was EB Private Equity. The offer, for full control of David Jones, valued the company at AU$1.65 billion (US$1.67 billion), the department store chain said. EB Private Equity’s website describes the firm as a Luxembourg and UK real estate and real estate-related investor, developer and private equity partner, focused on the United States, Asia and Africa. David Jones stock jumped more than 17 percent on the announcement, before easing to be 15 percent higher in late afternoon trade at AU$2.57. At that price, the company’s market value is AU$1.36 billion. The news also helped push other retail shares higher, with David Jones’ key rival Myer up nearly four percent at AU$1.60.