Computer hackers vandalized two more government sites on the Internet yesterday and left a taunting note promising to attack more federal computers because of a related FBI investigation.

Hackers from different organizations defaced an Interior Department Web page and a site run by a federal supercomputer laboratory in Idaho Falls, Idaho, claiming, "It's our turn to hit them where it hurts."

"These are the perils of open government," said Stephanie Hanna, an Interior spokeswoman. "We try to make as much of the materials of the Interior Department as open and available as possible. The consequence of that is, those who choose to do damaging things can do that."

Last week, hackers claiming to be from another group defaced the Web site for the U.S. Senate, causing it to be taken off-line until the weekend.

The FBI also was forced to take down its own Internet site last week after hackers launched an electronic attack against it. It remained inaccessible Monday, along with the Web site for its National Infrastructure Protection Center, which helps investigate computer crimes.

Messages left at the Interior and lab sites suggest they were vandalized to retaliate against what was said to be the FBI's harassment of specific hacker groups, including one that boasted of breaking into the White House site last month.

The FBI confirmed that it executed four search warrants last week in Texas related to an investigation into allegations of computer intrusion, including one search at the home of a prominent hacker in Houston.

On Interior's Web page, the hackers left this message: "Now, it's our turn to hit them where it hurts by going after every computer on the Net with a .gov [suffix]. . . . We'll keep hitting them until they get down on their knees and beg."

At the site maintained by the Idaho National Engineering and Environmental Laboratory, a note threatened the electronic destruction of the powerful computers that "serve" pages on the Internet "if the FBI doesn't stop."

"We could have done worse, like destroying completely all servers," the note said. "We can do it if we want, but hackers are waiting for Justice."

In an online interview, the hacker claiming responsibility for the laboratory attack warned that further FBI investigation would result in more severe damage.

The hacker identified himself only as M1crochip, living in Portugal and part of a group calling itself F0rpaxe. The interview was arranged through a mutually trusted third party.

"If FBI doesn't do anything and doesn't stop arresting people and making our life miserable, each member of F0rpaxe will discuss an eventual destruction of every single server," he said. "If that happens, everything goes down."

He added, "We don't want to proceed that way," and called the electronic attacks the "only resource" of the hacker community.