PARIS — Civilians are bearing the brunt of the fighting in Syria, Navi Pillay, the United Nations high commissioner for human rights, said Thursday, with 92,901 killings documented there through the end of April, a number that may understate the magnitude of the violence that has devastated cities and villages across the country for 25 months.

“The constant flow of killings continues at shockingly high levels,” Ms. Pillay said in a statement in Geneva, “with more than 5,000 killings documented every month since last July, including a total of just under 27,000 new killings since Dec. 1.”

Ms. Pillay cautioned that the analysis was conservative, and that “the true number of those killed is potentially much higher.”

President Bashar al-Assad’s forces started a bloody crackdown against largely peaceful protesters in March 2011, and defecting soldiers and other government opponents slowly began to take up arms. By fall of that year the conflict had begun devolving, and it is now a bitter civil war with increasingly sectarian overtones. But getting a clear picture of the conflict has been difficult, with few independent journalists able to report from inside the country, while the government and Syrian rebels and activists often issue contradictory reports of battles and massacres.

The latest study builds on an earlier report that found about 60,000 documented deaths through Nov. 30, 2012.

The new information was distilled from data provided by eight different sources, including human rights groups and Syrian activists. Mr. Assad’s government provided data only until March 2012, according to Rupert Colville, a spokesman for Ms. Pillay.

The initial pool of data showed a total of 263,055 reported killings. Analysts eliminated about 37,000 cases that did not include the victim’s full name, date and the location of death. They then crosschecked the verified deaths from the different lists to eliminate double-counting, a complex task owing to the way Arabic names may be rendered differently in different contexts.

The report was not able to break down the deaths by combatant and noncombatant, or pro- and antigovernment forces. But the numbers were telling, Ms. Pillay said in the statement. “This extremely high rate of killings, month after month, reflects the drastically deteriorating pattern of the conflict over the past year,” she said, and “civilians are bearing the brunt of widespread, violent and often indiscriminate attacks.”

“Government forces are shelling and launching aerial attacks on urban areas day in and day out,” she said, and are also using strategic missiles and cluster and thermobaric bombs. Opposition forces have also shelled residential areas, albeit using less firepower, and there have been multiple bombings resulting in casualties in the heart of cities, especially Damascus.

The largest number of killings has been recorded around Damascus, Homs, Aleppo and Idlib, and more than four out of five victims have been men. But the United Nations was unable to state definitively what proportion of those killed had been combatants.

Ms. Pillay said the killings of “at least 6,561 minors, including at least 1,729 children under 10 years old” were documented, and that there were “well-documented cases of individual children being tortured and executed, and entire families, including babies, being massacred — which, along with this devastatingly high death toll, is a terrible reminder of just how vicious this conflict has become.”

Ms. Pillay called for “an immediate cease-fire,” saying, “Nobody is gaining anything from this senseless carnage.”

She also urged the international community to help broker an end to the conflict. “The only answer is a negotiated political solution,” Ms. Pillay said. “Tragically, shamefully, nothing will restore the 93,000 or more individual lives already lost.”