U.S. companies added jobs at the slowest pace in three years in April, a private survey found, a sign that slower growth and volatile financial markets could weigh on hiring.

Payroll processor ADP says that businesses added 156,000 jobs in April, down from 194,000 in March. Manufacturers shed 11,000 jobs, after losing 3,000 the previous month. Services firms added 166,000, down from 189,000.

The slowdown was also driven by weaker hiring at medium and larger companies. Small businesses added jobs at the same pace as previous months.

The figures come just two days before the U.S. government's official jobs report. The ADP numbers cover only private businesses and often diverge from the official figures.

Economists forecast that employers added 200,000 jobs in April, while the unemployment rate remained 5 percent.