A closely monitored survey of business activity across the 19-country eurozone is showing that output growth in May has slowed to its weakest rate since early 2015.

Financial information company Markit says its flash composite purchasing managers' index — a broad gauge of business activity across the services and manufacturing sectors — has fallen to a 16-month low of 52.9 points in May from April's 53.0.

The reading is the latest in a series of indicators pointing to waning eurozone growth following a perky start to the year.

Chris Williamson, Markit's chief economist, says Monday that the survey, which is based on approximately 85-90 percent of normal final monthly replies, adds "further to the suggestion that the robust pace of economic growth seen in the first quarter will prove temporary."