MADRID, Spain - Spanish police have arrested five young computer hackers who allegedly disabled Internet pages run by government agencies in the U.S., Latin America and Asia, authorities said Saturday.

The National Police described the suspects as belonging to one of the most active hacker groups on the Internet and said two of the suspects are only 16 years old. The others are 19 or 20.

On the Internet, the group calls itself D.O.M Team, police said.

One of the group's techniques was to infiltrate Web sites and insert a page of its own, police said. A Google search turns up several hits with pages that fit this description.

The group attacked some 21,000 Web pages over the last two years, police said in a statement. The five were arrested this week in Barcelona, Burgos, Malaga and Valencia.

The statement did not identify which government Web sites the suspects are accused of tampering with.

The Spanish newspaper El Mundo reported in March that the group had infiltrated NASA's Web page, but a police official said Saturday she could not confirm this. The official spoke on condition of anonymity in line with department rules.

The group also hacked the Venezuelan national telephone company's page, and that of the Spanish telephone operator Jazztel, among others, the paper said.

El Mundo said it had contacted the group and it described itself not as a bunch of delinquents, but computer-lovers that raid Web sites to show system administrators the pages' vulnerabilities.

The Spanish investigation began in March after the Web page of a Spanish political party, Izquierda Unida, was disabled shortly after Spain's general election March 9.

The five suspects did not know each other personally, but rather just over the Internet. They were in contact with other members of the hacking group, mainly in Latin America, police said.