Factory activity in the U.S. mid-Atlantic region accelerated in December, bouncing back from the previous month's slump as new orders picked up.

The Philadelphia Federal Reserve Bank said its business activity index rose to 8.1 from minus 10.7 in November, easily topping economists' expectations for minus 3, according to a Reuters poll.

New orders climbed to 10.7 from minus 4.6.

Any reading above zero indicates expansion in the region's manufacturing sector. The survey covers factories in eastern Pennsylvania, southern New Jersey and Delaware.

It is seen as one of the first monthly indicators of the health of U.S. manufacturing leading up to the national report by the Institute for Supply Management.