Claims by first-time filers for unemployment insurance fell 44,000 to 434,000 last week, the Department of Labor said.
But the four-week moving average, which is seen as a more stable picture of the unemployment picture, rose 4,500 to 436,750. And economists had expected claims to drop by a further 4,000.
The increases are due to events that seasonal adjustment failed to take into account, said Bloomberg Businessweek: auto plants around the country shut down after the earthquake and tsunami in Japan, for example, and tornadoes caused higher than usual claims in Alabama.
Meanwhile, for the week ended April 23, 7.9 million people were receiving some form of unemployment benefits, a decrease of 31,000 from the prior week. 3.4 million of those receiving benefits had exhausted their regular benefits, which typically means they have been jobless for 27 weeks or more.