Google Inc. and other U.S. companies alleged that Turkey's telecommunications firms impersonated their servers to block access to social-media sites, as the ruling party tried to squelch dissent around local elections.

The telecom moves targeted sites like Twitter Inc. and YouTube, which Turkish Prime Minister Recep Tayyip Erdogan's detractors have used to organize and express dissent.

Sunday's decisive victories by Mr. Erdogan's ruling party renewed speculation that he will seek the presidency, which would extend his grip on power, and take revenge on his political enemies.

On Monday, Mr. Erdogan's rivals alleged vote-rigging and a political witch-hunt, a sign the election hasn't soothed the country's increasing polarization.

The weekend's results stunned his critics, as the opposition failed to check the premier's power amid the government's increasingly aggressive Internet blackout.