Nelson Chamisa, the national spokesman for the main opposition party Movement for Democratic Change, was fighting for his life last night in a Harare hospital after being ambushed in an airport departure lounge by plain-clothes agents wielding iron bars.

The assault and arrests, following on from threats to expel foreign envoys, marked a new clampdown from a government determined to strangle domestic dissent and prevent international support from reaching opposition groups.

Eyewitnesses said the senior member of the MDC was set upon by eight assailants who knocked him to the ground and administered a severe beating. Initial reports suggested Mr Chamisa's injuries were far worse than those suffered by the MDC leader Morgan Tsvangirai, in an incident that has drawn international condemnation of the Mugabe regime.

"[Mr Chamisa] was beaten on the head with iron bars. There was blood all over his face. He is in a critical condition at a private hospital in Harare," the party's secretary general, Tendai Biti, said from Johannesburg.

The assault came a day after Grace Kwinje and Sekai Holland, who were severely injured in last week's violence, were prevented from flying to South Africa to seek medical treatment. Professor Arthur Mutambara, leader of a MDC faction, was arrested as he attempted to fly to Johannesburg and was being held last night at a Harare police station.

Mr Biti said it was clear that Mr Mugabe did not want opposition leaders to give first hand testimony to the outside world. Mr Chamisa had been due to attend a meeting of the European Union and Africa Caribbean Pacific, in Brussels.

"Mugabe is clearly not relenting on violence against opponents," said Mr Biti. "All indications are that some in the opposition leadership will have to pay the ultimate price as this regime becomes more crude ... We won't be deterred however. The writing is on the wall for Mugabe."

On Saturday, agents from Mr Mugabe's secret police, the CIO, stole the body of Gift Tandare, an activist shot dead by police after the breakup of a peaceful prayer meeting last weekend. Mr Tandare's body was taken from a Harare morgue on Saturday where it was being prepared for burial. Authorities were concerned that his funeral would be a magnet for street protests.

The police also ignored a high court order to return Mr Tandare's body. Two lawyers, Otto Saki and Tafadzwa Mugabe, said high court judge Sam Kudya had ordered the police to produce the body, hand it over to his family and avoid interfering with his burial proceedings. The lawyers said that the court order was torn up and thrown in the bin by an assistant police commissioner when it was served.

Statements from Mr Mugabe in recent days have revealed deep divisions in his own party and suggested the autocratic leader has an insecure grip on a country he has ruled for the last 27 years. Speaking in Harare on Saturday, Mr Mugabe accused the opposition of resorting to violence sponsored by the former colonial power, Britain and other Western allies. "We have given too much room to mischief-makers and shameless stooges of the West. Let them and their masters know that we shall brook none of their lawless behaviour."

Analysts took the statement to be a coded reference to senior members of his own Zanu PF party, who have been in clandestine meetings with foreign envoys aimed at securing support for a transitional government if Mr Mugabe is toppled.

The 83-year-old president railed against what he called a "desperate and illegal plot to unconstitutionally change the government of the country".

The fact that Mr Mugabe has so far failed to secure unanimous cabinet support for declaring a state of emergency is the clearest indication yet of divisions in the ruling party. No move had been taken against the diplomats threatened with expulsion at the time of going to press.

Zimbabwe is facing a critical moment, Mr Tsvangirai said by telephone from Harare where he is recovering. "Things are bad," he told the BBC, "but I think that this crisis has reached a tipping point, and we could see the beginning of the end of this dictatorship in whatever form."

But the leader with the most leverage to rein in Mr Mugabe, the South African president Thabo Mbeki, remains silent.

Burial societies unite a shattered country

By Daniel Howden

In a divided country where political and racial differences have been exploited by a regime intent on staying in power, there is one thing that almost all Zimbabweans have in common: the burial society.

A kind of morbid Christmas club, these savings associations bring people together to meet the costs of burying their sons, daughters, sisters and brothers at a rate that is accelerating beyond comprehension.

A decent burial and a patient, ceremonial funeral - sometimes lasting for days - are integral parts of society in Zimbabwe and other African countries. Grieving relatives are obliged to meet the entertainment costs of the extended family, often running to hundreds of people for the duration of mourning. Failure to join a burial society means a pauper's funeral and the stigma that accompanies that.

On a typical Sunday morning, people in their best clothes will gather in the shade of a jacaranda tree, or in a vacant beer hall. They will bring their monthly subscriptions - no one wants to tempt fate by getting behind on payments - redeemable only when there is a bereavement in the family. But the economic unravelling of the country means meeting the costs of a dignified end has become impossible for most individuals and even most burial societies.

Zimbabwe now has the lowest life expectancy in the world: 37 for men and 34 for women. But these figures are based on data collected two years ago and researchers at the World Health Organisation admit the real figure could be as low as 30 by now. Zimbabwe has found itself at the nexus of an Aids pandemic, a food crisis and an economic meltdown that is killing an estimated 3,500 people every week.

Shenghi, a 26-year-old from the slums of Bulawayo, is typical: she has been forced to join two societies. What used to be a biannual event has now become a deluge, with death stalking every family. "In the past three months, we've had to bury 14 of the 50 people in our society," she says. She herself has lost four relatives in the past six months.

These societies are evolving into platforms for protest. The draconian laws drafted by Robert Mugabe's regime to eliminate all public space for dissent means that, for many Zimbabweans, the burial societies and related church groups are the only public gathering they can attend.

Hundreds draw together for the night vigil and the day of the funeral, and the police dare not break up such gatherings. People afraid to speak out elsewhere can voice their anger and despair freely. Pamphlets detailing alleged abuses by Mr Mugabe are often distributed and people share information in a society where newspapers and television outlets are under total government control.

This is why the regime has stolen the body of a murdered activist, Gift Tandare, to prevent a mass gathering for his funeral.