BUDAPEST (Reuters) - Hungary's top court said on Friday that a law proposed by Prime Minister Viktor Orban's ruling party forcing citizens to sign up in advance to be able to vote in national elections next year was unconstitutional.

After a review of the law asked for by President Janos Ader, the Constitutional Court also said in a statement that some of the law's provisions on political campaigns imposed "severely disproportionate" restrictions on the freedom of opinion and the media.

(Reporting by Gergely Szakacs and Krisztina Than; Editing by Louise Ireland)