NEW YORK — The decline in U.S. newspaper circulation is accelerating as the industry struggles with defections to the Internet and tumbling ad revenue.

Figures released Monday by the Audit Bureau of Circulations show that average daily circulation dropped 10.6 percent in the April-September period from the same six-month span in 2008. That was greater than the 7.1 percent decline in the October 2008-March 2009 period and the 4.6 percent drop in the April-September period of 2008.

Sunday circulation fell 7.5 percent in the latest six-month span.

As expected, The Wall Street Journal surpassed USA Today as the top-selling newspaper in the U.S. The Journal's average Monday-through-Friday circulation edged up 0.6 percent to 2.02 million, making it the only daily newspaper in the top 25 to see an increase.

USA Today saw its biggest decline, dropping more than 17 percent to 1.9 million. The newspaper has blamed reductions in travel for much of the circulation shortfall, because many of its single-copy sales come in airports and hotels.

The New York Times stayed in third place at 927,851, down 7.3 percent from the year-ago period.

Newspaper sales have been declining since the early 1990s, but the drop has accelerated in recent years, partly because newspapers have stopped serving harder-to-reach areas and have limited circulation to their core regions.

In many cases, people simply aren't buying print copies as much as they used to, given the abundance of free news on the Internet, often from the newspapers themselves. This has prompted newspapers to consider charging fees for Web access, but it could prove difficult to persuade people to pay for something they are used to getting for free.

The figures from the circulation bureau compare 379 daily newspapers and 562 Sunday newspapers that had reported average sales for both the current and year-ago periods.