OTTAWA -- Anonymous allegations that Canada's military police mistreated Afghan detainees five years ago will be investigated by the Military Police Complaints Commission, the agency announced Thursday.

The allegations suggest that the commanding officer at Kandahar Air Field ran exercises in empty detention cells next to those holding detainees in order to "terrorize" them and also that police went into cells in the middle of the night with weapons, pressed detainees against the wall and floor and applied arm locks.

The complainant also raised concerns about the military's own investigations into the incidents, including the fact that no charges were laid and no court martial convened.

"The allegation that the Military Police may have been involved in covering up misconduct ... is a very grave one that goes to the heart of the MPCC's mandate to ensure accountability for the MP and to foster public confidence in the availability of a suitable independent mechanism to investigate alleged misconduct," Hilary McCormack, chairperson of the commission, said in a statement.

The alleged incidents took place between December 2010 and 2011, but the complaint was not received by the commission until last February.

The commission said the person who sent in the complaint went to great lengths to conceal their identity, mailing a one-page, typewritten letter from the Sheraton Gateway Hotel at Pearson International Airport.

It included the names of five people listed as references for information about the incident and internal investigations and the commission contacted them before deciding to launch a review.

McCormack said the information obtained from them suggests there was a perception on the part of people deployed in Kandahar that some of the decisions made about the investigations were due to orders coming from "Ottawa" or because of concerns about the military's reputation in light of the attention that issues involving detainees can generate.

The fact the complaint was made anonymously is also important, McCormack said.

"Both the nature of the allegations and the manner in which the complaint was made tend to imply a lack of confidence on the complainant's part in the independence of the Military Police when investigating alleged misconduct by CAF members and in the ability of the Military Police to investigate themselves impartially," she wrote.

"Under the specific circumstances of this case, only an independent investigation could provide sufficient reassurance to the complainant and to others, so that in the future individuals are not dissuaded from stepping forward to voice their concerns or complaints due to fear of reprisals or lack of confidence in the mechanisms available to investigate such complaints."