ANKARA, Turkey (AP) — The European Court of Human Rights has rejected an appeal by Turkey's main opposition party challenging a referendum held earlier in the year that will increase the powers of the president.

The Strasbourg, France-based court ruled that the case did not fall under its jurisdiction, according to the decision published on Thursday.

President Recep Tayyip Erdogan's "yes" camp won the April 16 referendum on a series of constitutional amendments with a thin margin.

The opposition Republican People's Party, or CHP, contested the outcome of the vote, citing a number of alleged irregularities, including the Turkish electoral board's decision to count as valid unstamped ballots in violation of the law.

The CHP had applied to the European court after Turkish high court appeals were unsuccessful.