Tonderai Ndira will not be campaigning when Zimbabwe votes again. He will not rally his neighbourhood, as he did two months ago, for one last push against an unwanted regime. Instead, he is buried in an unmarked grave in the Warren Hills cemetery in Harare. A week on from his funeral, only his brother knows for sure which of the mounds is his. He will not leave a marker because he believes state agents are still not finished with the murdered activist. They would like to dig up his brother's remains to remove the incriminating evidence.

Mr Ndira's body was only found by accident in one of the capital's morgues a fortnight ago. His eyes had been gouged out and his tongue cut off. The 30-year-old was so badly beaten his father had trouble identifying him. A distinctive ring confirmed the identity of a man compared by some to South Africa's murdered rights activist, Steve Biko.

Mr Ndira, a lifelong campaigner for political change, had been arrested more than 30 times but kept up his opposition to the government that has led Zimbabweans to the lowest life expectancy in the world. His remains – a crushed skull, a bullet wound through the chest and blood-stained shorts – are a depressing metaphor for Zimbabwe in the aftermath of a stolen election.

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On 27 June, this bankrupt and terrorised country will go back to the polls. A wave of abductions, punishment beatings and murders of opposition activists is under way in an attempt to turn the outcome on its head and prolong the rule of President Robert Mugabe. This effort has entered a new phase and, while the bodies of the disappeared are starting to turn up in the mortuaries, more are being abducted all the time. At least 50 have died, 1,500 have been treated in hospital, 25,000 have been driven from their homes and countless more have lost their livelihoods.

David Coltart, an opposition senator, says violence in rural areas where the ruling Zanu-PF party did badly in the March poll, mainly in the north and north-east, has intensified. Speaking in London, the human rights lawyer said an estimated 25,000 people had been displaced in the past three weeks and the authorities had begun targeting individuals in the "second and third tier" of the opposition Movement for Democratic Change (MDC).

It was in this phase that Mr Ndira met his fate. His circumstances echo those of scores of others victimised in a state-sponsored campaign to beat the MDC into submission. A veteran of numerous arrests and internments, beatings and torture, Mr Ndira was accustomed to keeping on the move and staying one step ahead of the state security apparatus. Two weeks ago, suffering from exhaustion, he returned home to Mabvuku township outside Harare. Before dawn, say his family and other witness, a group of about 10 men, some masked and carrying Kalashnikov AK-47 rifles, appeared at his doorstep and demanded to see him. His wife called out to him and he asked the visitors to call back later. Instead, they burst into the activist's home and beat him in front of his two young children, before dragging him outside and into a truck, bloodied and still in his underwear.

In the weeks that followed his abduction, his family made frantic efforts to obtain any details about what happened to him. What took place can only be surmised by the unidentified, broken body that was found in a field in Goromonzi, 20 miles outside the capital, and taken to the mortuary at Harare's Parirenyatwa hospital. Mr Ndira was reportedly identified only after someone recognised the mutilated corpse from its tall and thin frame and guessed the rest.

It was a fate that would not have surprised the man himself. Interviewed by the BBC's Panorama programme in 2002, Mr Ndira said: "We are prepared to die. It is just the same, we are still dying in Zimbabwe. We are dying by hunger, by diseases, everything, so there is nothing to fear."

Fear is exactly what the Mugabe regime is counting on as it looks to overturn a first-round defeat that saw 56 per cent of the country voting against the only president they have known since independence, and saw his party lose its majority in the lower house of parliament. The octogenarian leader, who famously boasted that he has a "degree in violence", is relying on state security personnel backed up by paid militias to prevent a similar result in the run-off ballot.

The outcome of the first round was withheld for more than five weeks before the government conceded that Mr Tsvangirai had beaten Mr Mugabe by six points, though falling just short of an overall majority because a third candidate, Simba Makoni, took a small share of the vote.

A leading Zimbabwean army general has called on the nation's soldiers to vote for Mr Mugabe in the run-off or quit the military, the state-run Herald newspaper reported. The chief of staff, Major-General Martin Chedondo, told troops: "Soldiers are not apolitical. Only mercenaries are apolitical. We have signed up and agreed to fight and protect the ruling party's principles of defending the revolution. If you have other thoughts, then you should remove that uniform." He added that Mr Mugabe was head of the defence forces and "we should therefore stand behind our commander-in-chief". This echoes a similar statement by the joint chiefs of staff before the first round, in which they said they would not recognise any government other than that of Mr Mugabe, and they would refuse to salute Mr Tsvangirai if he won.

The MDC leader returned to Zimbabwe only last weekend, having stayed abroad for most of the past two months amid fears for his safety. On Friday, he gave what he called a "state of the union" address in which he called for a "new era of governance" in the country. Publicly, Mr Tsvangirai has said he remains confident that Zimbabweans will defy the intimidation campaign. However, there are serious concerns as to whether a democratic shift is at all possible. "We are witnessing the actions of a government which has thrown caution to the wind and will do anything to win the run-off," said Mr Coltart.

Despite this, he believes Mr Tsvangirai still has an "excellent chance" of defeating Mr Mugabe. In March, he said, the urban vote was low because of scepticism about the electoral process. The surprise result that time is likely to lead to a sharp increase in turnout in Harare and Bulawayo, increasing the overall vote by up to 300,000, most of which is likely to go to the MDC candidate.