MOSCOW Russian factory activity grew at the strongest rate in three months in August as new orders gained momentum, although the weak rouble added to the inflationary pressure facing manufacturers, a business survey showed on Friday.

The S&P Global Purchasing Managers' Index (PMI) for Russian manufacturing rose to 52.7 in August from 52.1 the month before, holding above the 50 mark that separates expansion from contraction for the 16th consecutive month.

"Manufacturing production continued to expand midway through the third quarter of the year on the back of solid new order growth," S&P Global said.

Growth in new orders quickened to a three-month high, with the related subindex climbing to 54.1 last month from July's 52.3.

Currency weakness pushed up manufacturers' input costs at the fastest rate in 17 months, leading them to also raise their own output costs at the quickest rate in over a year.

"Despite the overall improvement in operating conditions, manufacturers in Russia were faced with steep cost increases amid weakness of the rouble," S&P Global said.

Manufacturers took on more staff in response to the rise in new orders, although staff shortages and employees quitting slowed the overall pace of job creation to a nine-month low, the survey showed.

(Writing by Hugh Lawson; editing by John Stonestreet)