MOSCOW — Russian-backed rebels and Ukrainian government forces observed a cease-fire agreement on Tuesday to bring what officials called a “silent day,” at least one, to the now six-month war in eastern Ukraine.

The cease-fire was to coincide with the start of a new round of peace talks involving the European Union, Ukraine, Russia and separatists and set to take place in Minsk, the capital of Belarus. Though a dispute over the agenda delayed the talks, Ukraine and the separatists went ahead with the quiet day on the front all the same.

In a statement, Ukraine’s military said President Petro O. Poroshenko had ordered a cease-fire “along all positions of all forces in the counterterrorist operation,” as Ukraine refers to the conflict. Separatists issued similar avowals to hold fire.

The halt in shooting in fact merely honored, for one day, a cease-fire brokered three months ago, also in Minsk, on Sept. 5. That agreement unraveled immediately, and the subsequent fighting has killed an average of 13 people per day since, according to the United Nations. The Ukraine war has killed about 4,000 people since April and displaced about a million refugees.