The Australian bourse closed at its strongest in three weeks, rising more than 2 per cent, as a remarkably robust local economic data overshadowed a faltering US economy.

At 4:15pm (AEST), the benchmark S&P/ASX200 index finished at 4,495.7 points after gaining 91.5 points or 2.08 per cent. Meanwhile, the broader All Ordinaries index climbed 88.0 points or 1.98 per cent to 4,526.8 points.

All sectors were in the black, with materials up 2.5 per cent and financials ending 2.2 per cent higher.

On Wednesday's close of the Sydney Futures Exchange, the September share price index futures contract improved 103 points at 4,490 on volume of 39,211 contracts.

Only two companies in the S&P/ASX50 were in the red.

The Australian bourse had outperformed markets in Asia and Wall Street as economic data proved a strong local economy, according to Bell Financial Group senior adviser Chris Kimber.

Wednesday's finish for the S&P/ASX200 index was its highest since August 12 when it ended at 4400.9 points.

National gross domestic product (GDP) increased 1.2 per cent in the three months to June for an annual rate of 3.3 per cent, the Australian Bureau of Statistics said.

Economists predicted a quarterly rise of about 0.9 per cent for an annual rate of 2.7 per cent.

"Basically we are coupled still with America and we have been following them down regardless of the news in Australia," Mr Kimber said.

"The reason we have been underperforming (recently) is our economy has been doing well and confirmed it today that it is doing better than expected.

"GDP told us about the past and the Chinese PMI is telling us about the future."

Investors took heart in data indicating that China's manufacturers produced at a healthy clip in August as this assured them there was still strong demand for Australian commodities from Australia's largest export market.

The HSBC China Manufacturing PMI, or purchasing managers index, increased to a three-month high of 51.9 last month from 49.4 in July.

"The resources are particularly driving it (the Australian market)," Mr Kimber said.

BHP Billiton finished 86c or 2.32 per cent higher at $37.91. Rio Tinto moved up $2.15 or 3.07 per cent at $72.24.

The major banks were also stronger. National Australia Bank was leading with its shares gaining 65c or 2.8 per cent at $23.85.

ANZ ended 55c at $23.14 higher, while Commonwealth Bank edged up $1.01 at $51.31. Westpac finished 65c stronger at $22.35.