The military is under close scrutiny following its brief takeover in November that led to the resignation of former president Robert Mugabe.

Previous elections under Mugabe were marred by violence, intimidation and fraud -- often alleged to involve the security forces.

"The Zimbabwe Defence Forces has no direct role in the upcoming elections," said army spokesman Overson Mugwisi at a media conference in Harare ahead of the presidential, parliamentary and local polls.

"We are disturbed by false reports alleging that the Zimbabwe Defence Forces is going to be used by (the ruling) ZANU-PF to rig the posted vote."

Following the military's statement, the leader of the main opposition Movement for Democratic Change (MDC) party Nelson Chamisa said it would not participate in unfair elections and raised the prospect of calling for the election to be run by an outside body.

"We will not go into an election that has its own machinations," he said, casting doubt on the work of the Zimbabwe Electoral Commission but signalling his support for the military.

"We are going to be tempted to ask the South African Development Community (SADC) and African Union (AU) to take over" organising the vote, said Chamisa, referring to the regional and continental blocs.

- 'Violence-free but illegitimate election' -

He also called for the ZEC, which he has previously accused of being heavily staffed by regime supporters, to store and distribute ballot papers more transparently.

"We therefore call upon SADC, the AU and the international community to intervene and save a collapsing process and abate an imminent legitimacy crisis," he said.

The army appears to have staged its media briefing in response to a report in the Standard daily that it had deployed active service personnel to rural areas to campaign for candidates in ZANU-PF primary contests.

The Standard said it had received complaints from defeated contenders for the ZANU-PF slate.

They reported that some winning candidates who were former senior military officers had been "roping in the army to win the primary elections," it said.

"If some serving members are participating in the ongoing political campaigns, they will be doing so illegally and not as a result of an instruction from their commanders," said Mugwisi.

"The conduct of the Zimbabwe Defence forces after elections is going to be guided by the constitution."

July's polls will be the first ballot box test for Mnangagwa, and the first since Mugabe was forced to resign after 37 years in power.

President Emmerson Mnangagwa, 75, has pledged to hold free and fair elections as he seeks to mend international relations.

But the main opposition remains unconvinced by his stated commitment to democratic standards.

"What we are currently witnessing is a regime that simply talks but does not intend to hold credible elections. We are moving towards a violence-free but illegitimate election," added Chamisa.

But Chamisa signalled his faith in the military, saying he was "not worried".

"They are a patriotic army. They are a professional army, I work with the army very well. In fact, I respect them," he said.