CAIRO — The killing of an unarmed demonstrator by the police on Saturday threatened to stir up new protests here as Egypt’s military rulers and political parties braced for potential chaos surrounding the parliamentary elections scheduled to start on Monday.

An outpouring of anger over the episode, in which a protester was run over by a police truck, added to fears that continued protests and violence would undermine the integrity of the vote, the first since the ouster of President Hosni Mubarak nine months ago.

The episode took place at the end of a week of mounting protests across the country against Egypt’s interim military rulers, accused of threatening the revolution that brought down Mr. Mubarak by claiming permanent political powers and autonomy above a civilian government. The death recalled the event that set off the recent uprising, when the heavy-handed eviction of a small protest camp in Tahrir Square galvanized public anger against the military’s power grab.

That eviction set off days of clashes with the security police that left more than 40 dead and 2,000 injured, and it drew hundreds of thousands back to the square in recreations of the two-week sit-in that ousted Mr. Mubarak in February. Other protests continued around the country, including a demonstration by thousands in Alexandria, and on Saturday there were calls for major new demonstrations on Sunday or Monday.