MOSCOW — The Kremlin’s United Russia party and its three main allies maintained their lock on Parliament in national elections on Sunday, according to early results, with particularly low turnout in the largest cities.

The expected outcome will result in a business-as-usual State Duma, or lower house of Parliament, which has long supported President Vladimir V. Putin as he curbed civil liberties and sent the military on new foreign adventures.

Ella A. Pamfilova, the head of the Central Election Commission, announced that there were some reports of irregularities, but nothing excessive. Ms. Pamfilova, a respected human rights advocate newly appointed to the post, vowed to nullify the results if any obvious fraud — something of a tradition in previous elections — was detected.

Widespread perceptions of vote rigging in the last parliamentary election, in 2011, prompted mass street demonstrations, and the Kremlin, determined to avoid a repeat, seemed to try to make the entire campaign as uneventful as possible. It even moved the election date to September from December, apparently in the hope that many Russians would ignore the monthlong election season.