"The constant flow of killings continues at shockingly high levels -- 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]," Navi Pillay said in a release issued from Geneva, Switzerland.
"Unfortunately, as the study indicates, this is most likely a minimum casualty figure. The true number of those killed is potentially much higher."
The study, which updated an earlier report on 60,000 documented deaths through Nov. 30, 2012, was conducted using a combined list of 263,055 reported killings, identified by the name of the victim, and the date and location of the death. Any reported killing that did not include at least those three elements wasn't included on the list, which was compiled using information from eight sources.
After duplicates were merged, the combined number was reduced to 92,901 unique records of conflict-related deaths as of April, 30, 2013.
The analysis showed a marked increase in the average monthly number of documented killings since the beginning of the conflict, from about 1,000 a month in the summer of 2011 to an average of more than 5,000 per month since July 2012, the U.N. said.
"This extremely high rate of killings, month after month, reflects the drastically deteriorating pattern of the conflict over the past year," Pillay said.
She said both government forces and rebels were shelling urban areas.
Of the victims documented so far, 82.6 percent are male and 7.6 percent are female. The gender of the victim is not indicated in 9.8 percent of cases.
The analysis wasn't able to consistently to differentiate between combatants and non-combatants, and about 75 percent of the reported killings do not record the victim's age.
"I urge the parties to declare an immediate cease-fire before tens of thousands more people are killed or injured," Pillay said. "Nobody is gaining anything from this senseless carnage. ... The only answer is a negotiated political solution."