The online group Anonymous said Wednesday that it had paralyzed the Egyptian government’s Web sites in support of the antigovernment protests.

Anonymous, a loosely defined group of hackers from all over the world, gathered about 500 supporters in online forums and used software tools to bring down the sites of the Ministry of Information and President Hosni Mubarak’s National Democratic Party, said Gregg Housh, a member of the group who disavows any illegal activity himself. The sites were unavailable Wednesday afternoon.