NEW YORK (Reuters) - Online brokers E+Trade Group Inc. (NasdaqNM:EGRP - news) and Datek Online Holdings Corp. on Wednesday became the latest apparent victims of computer hackers who have wreaked havoc across the Internet this week.

E+Trade, the No. 2 U.S. online broker, and Datek, the fourth-largest, said that some of their customers were unable to log on to their respective sites after the routers the brokers used were overwhelmed by traffic.

It was the third day in a row that computer hackers appeared to have caused trouble on the Internet after attacking some of the most popular sites such as Yahoo! and Buy.com Inc. (NasdaqNM:BUYX - news) earlier this week.

``Access to the site was essentially clogged up,'' E+Trade spokesman Patrick DiChiro told Reuters, adding that less than 20 percent of the customers were unable to log on. E+Trade said its site had problems for more than an hour beginning at about 8 a.m. EST while Datek's problems lasted from 9:30 a.m. to 10:05 a.m. EST.

``It seems to be related to the 'denial of service' attack,'' Chief Technological Officer Peter Stern told Reuters, referring to the attacks on Yahoo! on Monday. ``I don't know if they were hackers, but I find it highly unlikely that someone just pulled the plug (on one of the routers).''

Routers direct traffic over telecommunications networks.

E+Trade and Datek said most of their customers had not had trouble logging on and those who did were rerouted.

``The site was never down, our site security was never compromised (and) customer accounts were never compromised,'' said E+Trade's DiChiro.

Meanwhile, Charles Schwab & Co. Inc. (NYSE:SCH - news), the No. 1 U.S. online broker, and Ameritrade Holding Corp. (NasdaqNM:AMTD - news) said they had not had any trouble so far.