BERLIN — At least three official German websites, including Chancellor Angela Merkel’s page, were inaccessible on Wednesday after an apparent cyberattack.

A group demanding that Germany sever ties with Ukraine and halt financial and political support for the government in the capital, Kiev, claimed responsibility for shutting down at least two sites, the chancellor’s and the website of the Bundestag, or lower house of Parliament.

A Foreign Ministry official later said that the ministry’s site was also inaccessible.

The sites were at least periodically inaccessible after about 10 a.m., according to Ms. Merkel’s spokesman, Steffen Seibert. Seven hours later, a government spokesman, speaking on the condition of anonymity, said that the attack was still being analyzed and that no comment could be made on the identity of the attackers.

Mr. Seibert earlier told reporters at a regular government news conference that “our service provider’s data center is under a severe attack that has apparently been caused by a variety of external systems.”