Virginia Rep. Frank Wolf says four of his computers were hacked. New Jersey Rep. Chris Smith says two of his computers were compromised in December 2006 and March 2007.
The two lawmakers are longtime critics of China's record on human rights.
In an interview Wednesday, Wolf said the hacking of computers in his Capitol Hill office began in August 2006. He says a computer at a House committee office also was hacked, and he suggested others in the House and possibly the Senate could be involved.
The FBI declined to comment.
Wolf said that in his office, the hackers "got everything," including all the casework regarding political dissidents around the world.
In comments to The Associated Press earlier in the day, Wolf suggested the problem probably goes further. "If it's been done in the House, don't you think that they're doing the same thing in the Senate?"
"I think this is very bad because you have the Chinese compromising and gaining access to computers of any number of members of the House and a major committee of the House," Wolf said. "We don't know how many others."
In calling for hearings in both the House and Senate, Wolf said there "probably are members serving in Congress whose computers have been compromised and they may not even know it."
Separately, U.S. authorities are investigating whether Chinese officials secretly copied the contents of a government laptop computer during a visit to China by Commerce Secretary Carlos M. Gutierrez and used the information to try to hack into Commerce Department computers.
The FBI declined to comment. In Beijing, the Chinese Ministry of Foreign Affairs had no immediate comment. Last week, China denied the accusations regarding Gutierrez's laptop and the alleged effort to hack Commerce Department computers.
Wolf said he has known about the hacking for a long time but was discouraged from discussing it publicly by people inside U.S. government, whom he refused to identify.
"The problem has been that no one wants to talk about this issue," said Wolf. "Every time I've started to do something I've been told 'You can't do this.' A lot of people have made it very, very difficult."
Wolf plans to introduce a resolution that he says will help ensure protection for all House computers and information systems. In a draft of prepared remarks he planned to deliver on the House floor Wednesday afternoon, Wolf says he is "deeply concerned that Congress is not adequately aware of or protected" from cyber attacks.
"My own suspicion is I was targeted by China because of my long history of speaking out about China's abysmal human rights record," Wolf says in his remarks. He said Congress should hold hearings, specifically the House Intelligence Committee, Armed Services Committee and Government Operations Committee.
Wolf's resolution calls for the chief administrative officer and sergeant at arms of the House, in consultation with the FBI, to alert House members and their staffs to the danger of electronic attacks. He also wants lawmakers to be fully briefed on ways to safeguard official records from electronic security breaches.
Speaking generally in May 2006, Wolf called Chinese spying efforts "frightening" and said it was no secret that the United States is a principal target of Chinese intelligence services.