GENEVA — The United Nations said on Friday that casualties in the fighting between Ukrainian government forces and pro-Russian rebels had doubled in the past month, with an average of 36 people killed every day.

At least 1,200 people were killed and 3,250 injured in the period from July 16 to Aug. 17, according to a report released by the Office of the High Commissioner for Human Rights in Geneva. The office described the toll as “very conservative” and said it did not include the 298 passengers and crew who died when Malaysia Airlines Flight 17 was shot down over eastern Ukraine on July 17.

“The trend is clear and alarming,” Ivan Simonovic, the United Nations assistant secretary general for human rights, said in Kiev, the Ukrainian capital, according to Reuters. “There is a significant increase in the death toll in the east.”

The upsurge in fighting concentrated around the rebel-held cities of Donetsk and Luhansk brought the total number of people killed in the clashes since mid-April to at least 2,220, and the number of injured to at least 5,956, the United Nations said, citing the reports of a 39-man monitoring mission working out of Kiev and four other cities.