New jobless claims rose unexpectedly last week on the back of layoffs after a series of tornadoes that struck the Midwest, a Labor Department report showed.

According to the report, claims for state unemployment insurance benefits rose 7,000 to 428,000 in the May 17 week from an upwardly revised 421,000 for the prior week.

Earlier this month, tornadoes swept through such states as Oklahoma, Missouri and Kansas, damaging automotive plants and other businesses, causing many job losses, the Department said.

The four-week average dropped for the second week in a row to 433,000 in the May 17 week from 440,750 in the previous week, its lowest in just over a month.

The number of people continuing to draw a week of benefits fell by 36,000 to 3.7 million.