PARIS - France's economy benefited in August from a pick-up in business due to the Olympic Games as a sharp upswing in the country's services sector offset ongoing weakness in manufacturing, a survey showed on Thursday.

The HCOB flash purchasing managers index for France's services sector, compiled by S&P Global, hit a 27-month high of 55.0 in August - up from 50.1 in July and beating a forecast for 50.3 in a Reuters poll.

Any figure above 50 points shows an expansion in activity, while below 50 indicates a contraction.

France, the euro zone's second-largest economy, has been banking on the Games to bolster its tepid growth rate. The country's statistics office has predicted a 0.3 percentage point boost from the Olympics, which ended earlier this month.

The flash composite PMI for August, which combines both the services and manufacturing sectors, rose to 52.7 points - a 17-month high - from 49.1 in July.

However, survey compiler S&P Global cautioned that the impact of the Olympics was likely to be temporary.

"Service providers will have benefited from the Olympic Games," said Hamburg Commercial Bank economist Norman Liebke.

"The one-off nature of this boost is evident in the worsening employment situation, weaker output expectations and declining backlogs of work," he added.

By contrast, France's manufacturing sector continued to weaken.

The flash manufacturing PMI figure for August stood at 42.1 - down from 44.0 in July and below a forecast of 44.4 in a Reuters poll.

(Reporting by Sudip Kar-Gupta Editing by Christina Fincher)