The big surge was a setback to hopes that layoffs were declining.
The Labor Department says that applications for unemployment benefits rose to 471,000 last week, up by 25,000 from the previous week. It was the first increase in five weeks and the biggest jump since a gain of 40,000 in February.
The forecast had been for claims to fall by around 4,000 from the previous week. The unexpectedly large rise in new claims underscored that even though the economy is growing, improvements in the labor market are coming in fits and starts.