NEW YORK (AP) _ CBS is shaking up its Internet division, laying off a quarter of its staff and bringing in new executives.

Twenty-four of the approximately 100 employees in CBS Internet Group were let go last week, company spokesman Dana McClintock said Tuesday.

In an internal memo, employees were told that ``as with all transitions, there comes a time when an organization must endure a certain amount of upheaval.''

CBS, which was recently acquired by MTV owner Viacom Inc., has had little to say publicly about its Internet strategy since forming the online division in January. The unit consists mainly of stakes in Internet companies like MarketWatch.com that CBS acquired by bartering advertising time.

CBS lured Russ Pillar from a senior marketing post at Virgin to head up the division, and Lisa Simpson, former chief of Sony's online effort, will be the chief operating officer.

On Tuesday Simpson brought over two other executives from Sony to work at CBS, one as chief technology officer and another as senior vice president of programming and production.

The shake-up comes at a turbulent time for young Internet companies, amid several high-profile flameouts such as retailer Boo.com.

On Monday, well-regarded news site APBNews.com fired all 140 people on its staff, and a number of others are believed to be near bankruptcy.