An Internet forum run by a loose international group that calls itself "Anonymous" directed participants to attack the websites of the Egyptian Ministry of Information and the ruling National Democratic Party. Neither was accessible from New York on Wednesday afternoon.
In a Twitter post, the group claimed credit for taking down the ministry's website and said the group was motivated by a desire to support Egyptian protesters.
The same group rallied to support WikiLeaks in November and December, attacking websites of companies it saw as hampering the document-distribution site.
The Egyptian government cut off all Internet service in the country on Friday, then restored it early Wednesday.
One member of Anonymous, speaking on condition of anonymity because of the possibly illegal nature of its activities, said the number of participants in the attacks was much lower than it was in December. Thousands of young people then joined in attacks on such sites as MasterCard.com and Visa.com - in those cases because the payment processors declined to transfer money to WikiLeaks.
But because the Egyptian government websites are much easier to take down, the lower number of participants is still adequate, the member said.
The member said the weapon of choice for the hackers is the same as in December: a small program called Low Orbit Ion Cannon. It sends out a flood of fake traffic to a selected website, swamping it if it doesn't have enough capacity.