The number of Americans filing new unemployment claims rose moderately last week, and there have been no signs so far that tightening credit conditions have had a significant impact on the labor market, which continues to face challenges. The Labor Department indicated on Thursday that initial claims for state unemployment benefits increased by 7,000 to a seasonally adjusted level of 198,000 for the week ending March 25. Reuters reported that economists had forecasted 196,000 claims for that week. Claims remain very low and are moving within a narrow range, despite layoffs from tech companies.