A Zimbabwean opposition spokesman and MP, Nelson Chamisa, was beaten unconscious yesterday at Harare airport as he was about to fly to Brussels, according to his party, the Movement for Democratic Change.

The attack followed the arrest of three other opposition leaders at the airport at the weekend and the snatching by government agents of the body of activist Gift Tandare, shot dead by police, to prevent a public funeral.

About 50 people including Morgan Tsvangirai, the opposition leader, were beaten and arrested while trying to attend a prayer rally eight days ago. Zimbabwe's president, Robert Mugabe, threatened more violence at the weekend, while Mr Tsvangirai pledged further resistance.

Mr Chamisa, 28, spoke to the Guardian from hospital where he was awaiting surgery late yesterday. Doctors said he may lose an eye from the assault, which took place in front of frightened travellers.

"Just as I was about to enter the door of the departure area, eight men jumped me and began hitting me with iron bars. I just fell to the ground," said Mr Chamisa. "Nobody is safe in Zimbabwe. There is no security, no rule of law. I am praying for my country."

Pearson Mangofa, an opposition MP who drove Mr Chamisa to the airport, said his assailants shoved away passengers who tried to help him. The men grabbed Mr Chamisa's passport, bags and laptop computer before speeding off in two cars, one without a licence plate.

Seven of them wore suits while one wore an army vest. Mr Mangofa said the attack bore the hallmarks of Zimbabwe's domestic spy agency, the Central Intelligence Organisation.

Mr Chamisa suffered "terrible injuries" to his head, jaw and right eye, said Mr Mangofa, who took him to hospital. Mr Chamisa already had injuries to his groin and head from beatings in police custody last week with Mr Tsvangirai and others. He was due to attend a European Union parliamentary conference in Brussels.

Two of the three MDC activists arrested at the airport on Saturday were attempting to leave the country for medical treatment for injuries received at the previous weekend's prayer rally. Sekai Holland and Grace Kwinjeh were taken by ambulance to the tarmac to board a flight to South Africa, but government agents seized their passports and took them back to the Avenues Clinic hospital, where they were under police guard last night.

Ms Holland, 64, has a broken arm, a broken leg and an infection in deep tissue injuries. Ms Kwinjeh, 30, has lost part of her ear lobe and has head injuries. The third person arrested was Arthur Mutambara, the leader of a breakaway faction of the MDC. He was being held by Harare police yesterday, according to lawyers who were seeking his immediate release.

At the weekend armed government agents seized the body of Gift Tandare, an MDC member who was shot dead by police on March 10. The men took Mr Tandare's coffin from a funeral parlour for a secret burial to prevent a public ceremony that had been scheduled for today and would have been attended by hundreds of mourners.

Mr Mugabe claimed that the UK and the US were backing the MDC in order to overthrow his government, according to the government-controlled Sunday Mail newspaper. "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," said Mr Mugabe, who warned that his government would be provoked to "measures which they will regret".

Mr Tsvangirai, however, said Zimbabwe was facing a critical moment that could bring positive change. "Things are bad, but I think that this crisis has reached a tipping point and we could see the beginning of the end of this dictatorship," he told the BBC.