Western nations are calling for increased sanctions against Zimbabwean officials, after the violent break-up of an opposition rally last weekend.
Mr Tsvangirai says his beating should be an inspiration to activists
The US said it was considering extending a travel ban and asset freeze, and the UK urged European governments to take similar measures.
Meanwhile Zimbabwe's government warned that anyone who incited violence to overthrow it would pay a heavy price.
Opposition activists were arrested and severely beaten after Sunday's rally.
Movement for Democratic Change (MDC) leader Morgan Tsvangirai, who had to be treated for a fractured skull, said the beating should be an "inspiration" for the opposition's struggle.
He said violence he and others endured at a police station was intended to inflict as much harm as possible.
But Zimbabwe's information minister said the injuries had been inflicted when Mr Tsvangirai and others attacked police.
Sikhanyiso Ndlovu told the BBC that police confiscated "killer" weapons from the activists, adding that four policemen were in hospital as a result of the attacks.
US State Department spokesman Tom Casey said extra sanctions were being considered against Zimbabwe following the arrests.
"We will have to take a look at what is currently on the table and what other steps might be taken. There's always other tools in the tool box," he said.
UK Prime Minister Tony Blair described the situation as a tragedy for the people of Zimbabwe.
"People should be able to live under the rule of law," he said.
"They should be able to express their political views without harassment or intimidation or violence. And what is happening in Zimbabwe is truly tragic."
Mr Blair was speaking after a meeting with Ghanaian President John Kufuor, who is currently chairman of the African Union.
Mr Kufuor said African leaders were embarrassed by the situation in Zimbabwe but rejected suggestions that they were unconcerned by the violence.
The action against Sunday's demonstration was also strongly condemned by the UN Secretary General, Ban Ki-moon.
But the most unexpected criticism came from South Africa, which urged Mr Mugabe to respect the rights of citizens, including opposition leaders.
BBC Africa editor Martin Plaut says that after years of fending off international pressure, Pretoria has adopted an entirely new tone.
The activists appeared in court - many bandaged and bruised - but were all then released from police custody after prosecution lawyers apparently failed to appear.
A number remained in hospital on Wednesday.
Mr Tsvangirai said he suffered head injuries, for which he received six stitches, and took "body blows" to the arms, knees and back, and that he lost two pints (one litre) of blood.
"There are lots of people who've been subjected to this kind of torture, this kind of brutality by this regime," he added.
A witness told the BBC the activists turned on police after one of their number was shot dead, but Mr Tsvangirai denied attacking the police.
"If there were any skirmishes, it was nothing to do with me," he said.
Civil discontent in Zimbabwe is rising over the country's economic crisis, with chronic unemployment and inflation running at more than 1,700% - the highest in the world.