Zimbabwe Doctors for Human Rights said the attacks began after the first round of presidential elections March 29 in which opposition leader Morgan Tsvangirai defeated Zimbabwean President Robert Mugabe, but not by enough to win outright and forcing a runoff, The Times of London reported Friday.

The humanitarian group said it has seen "a dramatic escalation" of violence during the past two weeks and has confirmed 22 deaths.

The organization said "violence is now on such a scale that it is impossible to document all cases," rendering the 900 figure a low estimate.

Of the 22 confirmed deaths, the organization said "at least double that have been reported but are yet to be confirmed," the British newspaper reported.

The Zimbabwe Election Commission made the results official last week. A runoff between Mugabe and Tsvangirai is supposed to be scheduled within 21 days of the official results but one election official said the runoff could be delayed up to a year.