WASHINGTON — More Americans sought unemployment aid last week, though the number of applications remains at a historically low level that is consistent with a healthy job market.

Weekly applications increased 10,000 to a seasonally adjusted 274,000, the Labor Department said Thursday. The four-week average, a less volatile figure, fell to a fresh 15-year low of 266,250.

Applications are a proxy for layoffs, so the very low readings indicate that most employees have solid job security.