Two of Japan's major Internet portals were hacked earlier this week, with one warning that as many as 100,000 user accounts were compromised, including financial details.

Goo, a Japanese Internet portal owned by network operator NTT, said it had no choice but to lock 100,000 accounts to prevent illicit logins. The company said it had confirmed some of the accounts had been accessed by non-users. The accounts can include financial details such as credit card and bank account information, as well as personal details and email.

The Web portal said it detected a series of brute-force attacks late Tuesday evening, with some accounts hit by over 30 login attempts per second. Goo said the attacks came from certain IP addresses, but didn't disclose any more information.

Also on Tuesday evening, Yahoo Japan said it discovered a malicious program on company servers. The program had extracted user data for 1.27 million users, but was stopped before it leaked any of the information outside of the company.

There was no immediate connection between the two incidents.

Yahoo Japan, owned by Softbank, is the country's dominant Internet portal and accounts for over 55 percent of search and portal use in the country, with hundreds of millions of page views per day, according to online service provider GA-Pro. The portal, operated separately from its U.S. namesake, has a strong mobile presence as parent Softbank also runs one of Japan's largest mobile operators. Rival Google accounts for about 42 percent.

Goo was extremely popular a decade ago as the Internet became popular in Japan, but has faded in recent years and currently accounts for less than 1% of Internet users. The site offers an array of portal services including search, mail and shopping.

Goo said it is still determining the scale of the damage from the attacks, while increasing its monitoring and asking users to pick more complicated passwords.

Yahoo Japan said it was taking the incident seriously and working to prevent reoccurrences.