French property giant Unibail-Rodamco announced Tuesday it will buy Australia's Westfield shopping mall operator in a deal worth US$24.7 billion to create "a global property leader", the two groups said in a statement.

The agreement would "create the world's premier developer and operator of flagship shopping destinations", they said.

Tuesday's announcement comes as mall operators embark on a consolidation drive as they face increasingly tough competition from online shopping sites such as Amazon, which this month launched in Australia.

Westfield's share price is down about 10 percent in 2017.

"The acquisition of Westfield is a natural extension of Unibail-Rodamco's strategy of concentration, differentiation and innovation," said Christophe Cuvillier, chief executive officer of Unibail-Rodamco.