The Australian currency reached a four-month high on Thursday noon after gaining almost half a US cent on the release of better-than-expected employment figures.

At 1200 AEST, the local dollar was changing hands at 92.18 US cents, up from Wednesday's close of 91.58 US cents. Since 7am, it has ranged from 91.72 to 92.34 US cents.

The Aussie received a lift from jobs data that showed the unemployment rate was a seasonally adjusted 5.1 per cent in August, declining from 5.3 per cent the month before, according to Nomura Australia economist Stephen Roberts.

''The strength of that employment number implies that there is a greater degree of certainty that the RBA (Reserve Bank of Australia) will be back to tightening before the end of this year,'' he said.

IRESS data shows the local unit last pushed above 92 on May 4 this year.

''It was helped (on Thursday ) also by the improvement in risk sentiment in markets overnight,'' Mr Roberts said.

The Australian unemployment rate decreased 0.2 percentage points to 5.1 per cent (seasonally adjusted) in August, according to official data released today.

The Australian Bureau of Statistics reported the number of people employed, rose by 30,900 people to 11.272 million (seasonally adjusted). Analysts had predicted it would decline l to 5.2 per cent.

Mr Roberts expects the local currency to rise further in afternoon trade.