U.S. job openings unexpectedly rebounded in August, as the labor market remains surprisingly resilient in the face of the Federal Reserve's aggressive interest-rate hike campaign.

The Labor Department said Tuesday there were 9.6 million job openings in August, a marked increase from the revised 8.92 million openings reported the previous month. 

Economists surveyed by Refinitiv expected a reading of 8.8 million.

"Any wonder why the Fed expects to raise interest rates again?" said Greg McBride, chief financial analyst at Bankrate. "With 1.5 job openings for every unemployed worker, there is little evidence of substantial easing in labor market demand, a risk to getting inflation lower."

This is a developing story. Please check back for updates.