The Australian stockmarket was half a per cent stronger at Wednesday noon, as higher prices for base metals and gold bolstered resources shares.

At 1205 AEST, the benchmark S&P/ASX200 index firmed 0.49 per cent to 4,649.4 points, while the broader All Ordinaries index lifted 0.47 per cent to 4,691.2.

The local bourse had hit a fresh four-month high, a good result given a mixed US lead, according to CommSec market analyst Juliette Saly.

"What has given a little bit of momentum to our market is news in the last 20 minutes or so that the Bank of Japan has intervened to weaken the strengthening yen, which has turned the Nikkei around and we're seeing some really good gains coming through from most Asian markets," she said.

Base metal prices on the London Metals Exchange overnight were all up between 0.3 per cent and 1.3 per cent.

In the mining sector, market heavyweight BHP Billiton jumped 0.10 per cent to $39.09 after Potash Corp said it was not considering a large stake sale to a third party or long-term production sharing agreements.

Fellow mining giant Rio Tinto added 0.02 per cent at $75.17 following announcement that its production at Laterriere Works aluminium smelter in Quebec will resume completely in a couple of weeks after a power outage.

Fortescue Metals, which an analyst suggested could overtake Rio and BHP in iron ore production by 2017, added 0.39 per cent to $5.04.

Gold miner Newcrest Mining lifted 2.05 per cent to $39.08, after gold soared more than 2 per cent overnight to a record above $US1,270 an ounce, its biggest one-day gain in four months.

National Australia Bank led gains among the big four, jumping 1.75 per cent to $25.66 after it abandoned its $13.3 billion bid to take over the Australian and New Zealand businesses of wealth manager AXA Asia Pacific Holdings.

Commonwealth Bank had inched 0.13 per cent to $53.67, Westpac was up 0.85 per cent at $23.57 and ANZ was 0.54 per cent higher at $24.15.

Australia's largest investment bank, Macquarie Group, swelled 1.42 per cent to $36.21.