PARIS (AP) — The owner of Westfield shopping centers is being bought by French property investor Unibail-Rodamco for $15.7 billion as shop retailers struggle to keep up with the move to online sites like Amazon.

The companies said Tuesday that the cash and shares deal would create a company with 104 shopping centers in 13 countries that bring in an estimated 1.2 billion visits a year.

Unibail-Rodamco invests in commercial property, from malls to office space, mainly in mainland Europe. Westfield, which started off in Sydney in the 1950s, is known for its 35 upscale shopping centers in major metropolitan areas, particularly in the U.S. and Britain.

Unibail-Rodamco SE said Tuesday that its offer values Westfield shares at $7.55 each, a premium of 17.8 percent on Monday's closing price. Based on the number of outstanding shares, that values the takeover at $15.7 billion.

The deal is part of a wave of takeovers and acquisitions in the retail property industry as sales decline.

"The industry is under severe pressure from internet selling and particularly Amazon," said John Colley, a professor at the Warwick Business School. "As sales fall so do retail property prices to the point where they become attractive as a discount to asset value."

Frank Lowy, Westfield's chairman, said "the transaction announced today is the culmination of the strategic journey Westfield has been on since its 2014 restructure."

In the new company, Lowy would chair an advisory board while the CEO of Unibail-Rodamco, Christophe Cuvillier, would retain that role.

The deal was recommended by the boards of both companies but is subject to approval by shareholders and regulators.