New claims for unemployment benefits unexpectedly rose last week, the second consecutive week of climbing claims.

The Department of Labor said that there were a seasonally adjusted 351,000 initial claims for state unemployment benefits in the week ended September 18, up from 335,000 in the previous week.

The four-week moving average—which smooths out short-term volatility—fell by 750 to 335,750. The previous week’s average was revised up by 750 to 336,500.

The rising number of new claims, which are a proxy for layoffs, raises the risk that progress in the labor market may have stalled as the economy suffers the one-two punch of supply chain disruptions and the Delta variant.

Continuing claims rose 131,000 to 2,845,000. The previous week’s level was revised up 49,000 from 2,665,000 to 2,714,000.