SYDNEY (Reuters) - Macquarie Group Ltd (>> Macquarie Group Ltd), Australia's top investment bank, said it jointly bought the country's largest owner of mobile telephone towers from a business owned by U.S. wireless infrastructure giant Crown Castle International Corp (>> Crown Castle International Corp).

The Macquarie Infrastructure and Real Assets fund joined local pension fund Unisuper and a UBS AG (>> UBS AG) fund to buy Crown Castle Australia Holdings Pty Ltd, the company said, without disclosing a price.

The Australian Financial Review reported the Macquarie consortium paid A$2 billion ($1.62 billion) for the business, or 20 times annual earnings. Macquarie did not immediately respond to a call for comment.

The purchase underscores the interest in telecommunications infrastructure in Australia where demand for high-speed internet is growing rapidly. Earlier this month, internet provider iiNet Ltd (>> iiNet Limited) agreed to a A$1.6 billion takeover proposal from rival TPG Telecom Ltd (>> TPG Telecom Ltd).

It also shows Macquarie is sticking with its strategy of limiting its exposure to volatile markets and investing in relatively low-risk, annuities-style assets with stable returns.

"The (Crown Castle) business has the qualities that infrastructure investors around the world seek: stable revenues backed by long-term customer contracts, predictable cashflows, strong operating margins and growing customer demand," Macquarie Infrastructure's co-head of Asia Pacific, Frank Kwok, said in a statement.

Crown Castle Australia has about 1,700 wireless towers that are used by the country's largest telecommunications companies to "provide communications infrastructure for the vast majority of mobile device users in Australia", Macquarie said.

The consortium would fund the purchase as an equity investment with third-party debt finance, it said.

(Reporting by Byron Kaye; Editing by Richard Pullin)