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Aug 9 (Reuters) - Australia's Suncorp Group (SUN) posted an 86.3% rise in its full-year cash earnings on Wednesday, on the back of improved underlying margins and a significant turnaround in investment returns.

Also aiding the cash earnings, the company logged strong top-line growth across the group's Insurance Australia and banking arm for the year ended June 30.

The country's second-biggest insurer by market value posted annual cash earnings of A$1.25 billion ($817.38 million), compared with A$673 million a year earlier.

Net gain from yields and investment markets was A$724 million for the year, compared with a loss of A$190 million in 2022, the company said in a statement.

Last week, the company's A$4.9 billion banking arm sale to ANZ Group Holdings (ANZ) was blocked by the country's competition regulator.

Suncorp now expects the separation and other costs related to the deal to increase from A$500 million to between A$575 million and A$600 million.

The company also declared a final dividend of 27 Australian cents per share, compared with 17 cents per share a year earlier.

($1 = 1.5295 Australian dollars)