The number of Americans seeking initial jobless benefits jumped by 18,000 last week, the government said on Thursday, but it attributed the entire rise to the effects of hurricanes that have battered the southern United States. First-time claims for state unemployment insurance rose for the third straight week, climbing to 369,000 in the week ended Sept. 25 from a revised 351,000, the Labor Department said. The rise defied Wall Street economists' expectations for a fall to 340,000 from the prior week's original measure of 350,000. "All of the increase in weekly claims was attributed to hurricanes," a spokesman for the Labor Department said. The most recent -- Jeanne -- was the fourth violent storm to strike Florida in six fraught weeks that began when Charley pummeled the Sunshine state in mid-August. The hurricanes' impact has skewed the weekly claims numbers for several weeks and data have yet to show the effects of Hurricane Jeanne, which struck after the current reporting week. The Labor Department said the storms have also affected the closely watched four-week moving average, seen by many economists to be a more accurate barometer of labor trends because it irons out the weekly fluctuations. The four-week average rose for the third straight week, hitting 343,500, up from 341,250 in the previous week.///www.reutres.com