SEOUL, South Korea (AP) - Suspected cyber attacks paralyzed Web sites of major South Korean government agencies, banks and Internet sites in a barrage that appeared linked to similar attacks in the U.S., South Korean officials said Tuesday.

The sites of the presidential Blue House, the Defense Ministry, the National Assembly, Shinhan Bank, Korea Exchange Bank and top Internet portal Naver went down or had access problems since late Tuesday, said Ahn Jeong-eun, a spokeswoman at Korea Information Security Agency.

The alleged attacks appeared to be linked to the knockout of service of Web sites of several government agencies in the United States, Ahn said.

The U.S. sites were hit by a widespread and unusually resilient computer attack that began July 4, The Associated Press has learned.

In the United States, the Treasury Department, Secret Service, Federal Trade Commission and Transportation Department Web sites were all down at varying points over the holiday weekend and into this week, according to officials inside and outside the government. Some of the sites were still experiencing problems Tuesday evening.

Some of the South Korea sites remained unstable or inaccessible on Wednesday morning.

The paralysis took place because of denial of service attacks, in which floods of computers all try to connect to a single site at the same time, overwhelming the server that handles the traffic, the South Korean agency said in a statement.

Ahn said there have been no immediate reports of financial damage or leaking of confidential national information from the alleged cyber attack, which appeared aimed only at paralyzing Web sites.

South Korea's Defense Ministry said Wednesday that there has been no leak of key military information.