Robert Mugabe's Government warned Zimbabwe's opposition today that they would pay "a heavy price" for their so-called campaign of violence to oust the leader from power.

Morgan Tsvangirai, who heads the biggest faction of the Movement for Democratic Change (MDC), was said today to be in intensive care after suffering a suspected skull fracture while in police custody.

The scale of the police violence became clear as 50 opposition leaders and supporters were released from court following their arrest over a banned rally on Sunday.

Mr Mugabe's controversial rule is once again under the spotlight as Zimbabwe sinks deeper into its economic crisis – with inflation at 1,700 per cent.

However, the Government was today unapologetic and suggested that Mr Tsvangirai and his supporters had been beaten for resisting arrest.

“Those who incite violence, or actually cause and participate in unleashing it, are set to pay a very heavy price, regardless of who they are,” Sikhanyiso Ndlovu, the Information Minister, said in a statement.

"The Tsvangirai faction of the MDC has a long record of unleashing violence to achieve political goals. It has publicly restated its wish to use violence to overthrow Government and as a means to power. This will come to grief."

The Government accused the opposition of organising illegal meetings and protests, inciting anti-government violence in townships and encouraging criminal attacks on police officers, arson and looting.

“In particular, Government has noted the MDC leadership’s publicly announced mission to seek to topple the government through civil unrest in order to realise the British-led goal of ’regime change’ in Zimbabwe,” Mr Ndlovu said.

He accused Western governments, including Britain and the United States, of making “unconditional statements of support to the violent MDC”.

Meanwhile, campaigners took to the streets of London as John Agyekum Kufuor, the Ghanaian President and African Union chairman, attended a meeting to mark 50 years of independence.

Protestor Alois Mbawara, 25, of the group Free-Zim Youth, said “I went on to the stage to make my protests. We have been driven to ambush them because diplomatic means are not working.

“The President is also president of the African Union and we need them to put pressure on Mugabe. They’re not doing anything."

Mr Kufuor said today that African leaders were embarrassed by the situation in Zimbabwe, but had failed to have influence because of stiff resistance from Harare.

“The African Union is very uncomfortable. The situation in your country is very embarrassing,” Mr Kufuor said in response to a question from a Zimbabwean at the meeting at Chatham House.

“I know personally that presidents like [Nigeria’s Olusegun] Obasanjo, [South Africa’s Thabo] Mbeki and others have tried desperately to exercise some influence for the better. But they came against stiff resistance."

Mr Kufuor stressed that African leaders were serious about tackling the situation in Zimbabwe, but that individual nations were limited by what unilateral action they could take.

“What can Mbeki as a man, alone, do against Zimbabwe?” said Mr Kufuor. “In our own various ways we are trying very hard to exercise some influence ... I tell you, we are serious.”

The media was less sympathetic. Johannesburg's The Star newspaper printed a cartoon showing Mr Mbeki sitting smugly in an armchair with a pipe, saying: “Bob old chap, I don’t mean to interrupt, but ... um ... when you do have a minute...” as Mr Mugabe truncheons Mr Tsvangirai.

Times Recommends

• Zardari still has to tackle tough questions
• Material evidence 'debunks' Turin Shroud
• BBC criticised over Uganda gay execution poll