A closely-watched survey shows employers in the eurozone hiring extra staff at the fastest rate in four years even though growth momentum waned in May for the second straight month.

Financial information company Markit said Thursday that employers remain upbeat about the outlook, especially in manufacturing where the weaker euro has helped drive strong export sales.

However, it noted "worrying signs of confidence waning" in the service sector compared with the optimism seen earlier in the year.

Overall, Markit said, business growth needs to rebound to persuade companies to continue hiring at anything like the rate seen in May

Its headline gauge of business activity — the purchasing managers' index — fell to a three-month low of 53.4 in May from 53.9 the previous month. Anything above 50 indicates expansion.