Zimbabwe's President Robert Mugabe said the car crash that killed Prime Minister Morgan Tsvangirai's wife was "the hand of God", speaking at a funeral service on Tuesday.

"It will take him time to recover from this shock. I plead with you to accept it, it's the hand of God," Mugabe told hundreds of mourners gathered at a Methodist church in Harare.

The remarks were Mugabe's first public comments on the crash that killed Susan Tsvangirai and injured her husband on Friday.

An oncoming truck hit their 4x4 on a potholed highway outside Harare, sending their vehicle flipping off the road.

Mugabe and his wife Grace visited Tsvangirai in hospital shortly after the collision, which had sparked speculation that the crash was linked to a long history of political leaders dying in suspicious accidents.

Mugabe, whose supporters staged deadly attacks against Tsvangirai's Movement for Democratic Change (MDC) around last year's elections, said it was time for Zimbabwe to move past the violence.

"We are doing our best that we create a conducive environment and tell our supporters that the issue of violence must end," he said.

"Rest assured we are with you, honourable prime minister. Our hearts on this day and the days to follow, we are with you," he added.

Susan Tsvangirai is to be buried on Wednesday.

Mugabe and Tsvangirai formed a unity government four weeks ago in a bid to end a year of political turmoil and pull the country from economic ruin, but their coalition has been dogged by doubts due to the arrest of a top Tsvangirai aide and disputes over top political appointments.