The Australian stockmarket maintained a four-month high on Tuesday noon following positive offshore leads and better-than-expected results from a domestic business confidence survey.

At 12.06pm AEST, the benchmark S&P/ASX200 index was 24.1 points or 0.52 per cent higher at 4639 points. The broader All Ordinaries index had added 26.2 points or 0.56 per cent to 4680.4 points, the highest since early May.

Mining stocks took charge, with the minerals sector increasing 1.1 per cent. Energy put in 0.7 per cent and financials went up 0.4 per cent.

On the Sydney Futures Exchange, the September share price index contract climbed 10 points at 4642 points on a volume of 60,715 contracts.

Australian business sentiment returned to levels last seen in April as profits increased although sales and employment conditions weakened, according to a National Australia Bank Ltd survey of more than 530 companies from Aug. 24 to Aug. 31.

"Business confidence rebounded 9 points in August, following three months during which overseas financial turbulence and policy uncertainty contributed to more subdued readings," NAB said.

CMC Markets market analyst David Taylor said the National Australia Bank's monthly business confidence was slightly better-than-expected.

"The fact that interest rates haven't moved up for some time and we know that there's quite a squeeze on labour costs at the moment, I'm not surprised to see that confidence figure moving up."

"Defensive stocks are not in favour at midday today but other cyclical stocks are in favour, with mining, energy and finance stocks still doing quite well."

Among mining stocks, market heavyweight BHP Billiton took in 48 cents at $39.04 at 12.07pm AEST. Rio Tinto had added 41 cents to $75.71 and Fortescue Metals Group had edged up six cents to $5.03.

Of the financials, National Australia Bank improved 13 cents at $25.35, while Commonwealth Bank lifted 31 cents to $53.82. Westpac had looked up 10 cents to $23.49 and ANZ was 13 cents stronger at $24.14. Macquarie Group gained 47 cents to $35.72.