Turkey's Western allies have voiced deep concerns over media intimidation in the run-up to the election that returned President Recep Tayyip Erdogan's party to power. The surprise outcome of Sunday's vote could further entrench power in the hands of Erdogan, the dominant figure in Turkish politics for more than a decade who critics warn is becoming more autocratic. In a turnaround that confounded pollsters, Erdogan's Islamic-rooted Justice and Development Party (AKP) reclaimed the majority it lost just five months ago, returning the Muslim majority country to single-party rule once more. Erdogan on Monday declared the outcome a vote for "stability" after renewed conflict with Kurdish rebels and a wave of bloody jihadist attacks, and called on the entire world to respect the result. But the United States, a key ally, and two European observer missions expressed concern over the campaign, particularly the crackdown on media critical of Erdogan. White House spokesman Josh Earnest said the US was "deeply concerned that media outlets and individual journalists critical of the government were subject to pressure and intimidation during the campaign". "We have both publicly and privately raised our concerns about freedom of the press, freedom of speech and freedom of assembly in Turkey," he said. His remarks echoed the findings of European election observers. While voters were given a choice between genuine alternatives, "the rapidly diminishing choice of media outlets, and restrictions on freedom of expression in general" caused "serious concerns," said Ignacio Sanchez Amor, head of an Organization for Security and Cooperation in Europe mission. "Unfortunately, the campaign for these elections was characterized by unfairness and, to a serious degree, fear," said Andreas Gross, head of the Parliamentary Assembly of the Council of Europe (PACE) delegation. 35 Gulenists arrested Turkish police on Tuesday detained 35 suspects including high-ranking bureaucrats and police officers as part of a probe into supporters of a US-based cleric accused of plotting to bring down President Erdogan, local media reported. Police raided several addresses in the western coastal city of Izmir, the private Dogan news agency reported. The operation comes just after Erdogan's AKP swept back to power by winning almost half of the vote in Sunday's election. A strengthened AKP government is expected to speed up efforts to clean the state of exiled Turkish cleric Fethullah Gulen's loyalists. A former ally of Erdogan turned arch-enemy who lives in the United States, Gulen is charged with "running a terrorist group" which launched a probe into the president's inner circle in 2013. He is due to go on trial in absentia in January. Erdogan accuses Gulen of trying to topple him by persuading allies in Turkey's police force and judiciary to launch a vast probe into government corruption in December 2013, which led to the resignation of four ministers. Turkish authorities responded by purging both the police force and judiciary of pro-Gulen elements and arresting news editors and businessmen. Meanwhile, Prime Minister Ahmet Davutoglu called on all parties to agree on a new civilian constitution to replace a 1980 military-drafted charter. "Let's work together toward a Turkey where conflict, tension and polarization are non-existent," he told thousands of supporters on election night.