The number of people filing initial applications for US state unemployment benefits fell sharply last week, the government reported Thursday, offering further evidence that recent strong job gains may continue. The Labor Department said jobless claims fell 21,000 last week to 283,000. The four-week moving average of claims, a less volatile measure, fell 6,500 to 289,750, its lowest level in 15 weeks. Jobless claims, a measure of layoffs, have been near or below 300,000 since September, a low level by historical standards that indicates solid hiring. Average weekly claims have fallen 16 percent in the last 12 months, and they are near 14-year lows. More than 3.2 million jobs have been created in the past year, helping to lower the national unemployment rate to 5.7 percent in January from 6.6 percent a year earlier.