A respected European body of international election observers declared Monday that Turkey’s controversial Sunday referendum was held on an “uneven playing field,” calling into question the fairness of the vote that narrowly handed sweeping new executive powers to President Recep Tayyip Erdoğan. In a statement, the Organization for Security and Co-Operation in Europe said impartial information about what the reforms would do was not made available to voters and the arrests of journalists and news outlet closures had a “negative effect” on the process. While he cited no specific problems at polling places, delegate Cezar Florin Preda said the referendum did not live up to Council of Europe standards. “The legal framework was inadequate for the holding of a genuinely democratic process,” he said in the statement. Civil-society groups have put the number of reporters arrested since last summer’s attempted coup against Erdoğan at nearly 160. Separately, the head of Turkey’s electoral body declared the results valid, showing Erdoğan with 51 percent of the vote. The main opponents to the reforms, the Republican People’s Party, or CHP, have cited irregularities in the referendum and demanded a recount of 60 percent of the votes. Demonstrations took place all over the country to protest the vote.