Zimbabwe's army has been accused of supplying militants with weapons to intimidate voters to ensure Robert Mugabe wins a possible run-off in the presidential election.
Human Rights Watch said in a statement that military forces had equipped war veterans with weapons and trucks to scare Zimbabweans into backing President Mugabe.
The group called on the African Union and the UN Security Council to take immediate steps to prevent an escalation of violence.
Morgan Tsvangirai's Movement for Democratic Change has accused Robert Mugabe of unleashing militias to help him rig victory and activating veterans of the independence war.
They have used violence in the past to support the former guerrilla leader.
The MDC has said at least 15 party members have been killed by ZANU-PF. The government denies accusations that it has launched a violent campaign against opponents in the post-election crisis.
The UNSC took up Zimbabwe's election standoff for the first time yesterday, and Western powers pressed for a UN mission or envoy to visit the crisis-stricken southern African country.
Vote checking from Zimbabwe's 29 March presidential poll was put off again on Tuesday, further delaying when the world will know if Mr Mugabe will remain in power.
