The global manufacturing downturn gathered pace in August, with output and new orders falling at their fastest in over three years, a business survey showed on Tuesday.

The JPMorgan Global Manufacturing PMI fell to 48.1 in August from 48.4 in July, its lowest reading since June 2009 and dipping further below the 50 threshold that signifies growth.

"The August PMIs point to a further modest acceleration in the rate of contraction of global industry, as the sector is buffeted by rising headwinds in a number of key economic regions and falling levels of international trade," said David Hensley at JPMorgan.

The new orders index fell to 46.8, the lowest since April 2009, pushing factories to reduce staffing levels for the second month.

The U.S. ISM survey, released earlier on Tuesday, showed the American manufacturing economy shrank at its sharpest clip in more than three years in August, against expectations for stagnation.

The eurozone manufacturing sector contracted faster than previously thought last month but Britain bucked the trend by posting a surprise rise in its PMI - although it still showed contraction.

China's official PMI fell below 50 for the first time since November, while a similar survey from Markit, sponsored by HSBC, showed activity shrinking at its fastest pace since March 2009, figures showed on Monday.

The index combines survey data from countries including the United States, Japan, Germany, France, Britain, China and Russia.