Nielsen BookScan said the figures for "Harry Potter and the Deathly Hallows" were provisional; full and final figures were due to be released Tuesday.
The company said 2.6 million copies of "Deathly Hallows" were sold in Britain in the 24 hours after it went on sale in England at 7:01 p.m. EDT Friday. The figure breaks the previous record of just over 2 million copies held by the previous Potter volume, "Harry Potter and the Half-Blood Prince." It includes sales from book stores, supermarkets, other retailers and Internet sites, but excludes sales to libraries, schools and institutions.
"Deathly Hallows," the seventh and final volume of J.K. Rowling's all-conquering fantasy series, sold 8.3 million copies in its first 24 hours on sale in the United States, according to publisher Scholastic Inc.
Photos: Harry Potter Fans
The book was released around the world Saturday in a carefully orchestrated operation that saw midnight book store openings and long lines of Potter-maniacs. Its initial print run was 12 million in the United States alone.