A law that enabled Russian oligarch Roman Abramovich to become a Portuguese citizen due to his alleged ascendancy from Sephardic Jews has been altered but the changes will not be retroactive, the foreign minister said on Wednesday.

"The decree introduces a requirement for (applicants to have an) effective connection with Portugal," Foreign Minister Augusto Santos Silva said, describing it as a "mechanism" to prevent the law to be "manipulated."

(Reporting by Catarina Demony, editing by Inti Landauro)