US consumer prices accelerated in August amid a jump in the cost of petrol and rental accommodation, new figures show today.

The increases are signs of firming inflation that could allow further monetary policy tightening from the Federal Reserve this year. 

Other data today showed an unexpected drop in the number of Americans filing applications for unemployment benefits last week. 

Though the data was impacted by hurricanes Harvey and Irma, the labour market remains healthy with increasing reports of worker shortages in some industries. 

The Labor Department said its consumer price index rose 0.4% last month after edging up 0.1% in July. 

August's gain was the largest in seven months and lifted the year-on-year increase in the CPI to 1.9% from 1.7% in July. 

Economists had forecast the CPI rising 0.3% in August and climbing 1.8% year-on-year. The Labor Department said Harvey had a "very small effect on survey response rates in August." 

Today's inflation figures showed that petrol prices surged 6.3%, the biggest gain since January, after being unchanged in July. 

Further increases are likely in September after Harvey forced temporary closures of refineries. 

Department officials said it was difficult to say whether the storm, which slammed Texas towards the end of August, impacted on petrol prices last month.

Stripping out the volatile food and energy components, consumer prices increased 0.2% in August. That followed four monthly increases of 0.1% in a row. 

In the 12 months through August, the so-called core CPI rose 1.7%. The year-on-year core CPI has now increased by the same margin for four consecutive months.

Economists expect the Fed will announce a plan to start reducing its $4.2 trillion portfolio of Treasury bonds and mortgage-backed securities at its September 19-20 policy meeting. 

Low inflation, despite the labour market being near full employment, is seen causing the Fed to delay raising rates for a third time this year until December. 

In a second report today, the Labor Department said initial claims for state unemployment benefits declined 14,000 to a seasonally adjusted 284,000 for the week ended September 9. 

Claims have now been below 300,000, a threshold associated with a robust labour market, for 132 consecutive weeks. 

That is the longest such stretch since 1970, when the labour market was smaller. Economists had forecast claims rising to 300,000 in the latest week.