In a speech in Berlin on the 60th anniversary of the Universal Declaration of Human Rights, Merkel added her voice to a growing chorus of calls in the West and Africa for Mugabe to finally quit.
"The excuse of national sovereignty cannot be used to shelter the completely unrestrained commission of serious human rights breaches," Merkel said.
"Especially in Zimbabwe’s case, we must do our very best to attain life without the terrors of President Mugabe," she said.
Her appeal echoes a string of calls recently by world leaders, including US President George W Bush, British Prime Minister Gordon Brown, French President Nicolas Sarkozy and Kenyan Prime Minister Raila Odinga for Mugabe to relinquish his 28-year hold on power.
Rowan Williams, the Archbishop of Canterbury and head of the Anglican Church, also jumped into the fray, saying "outside pressure" on Mugabe’s regime was now "more necessary than ever".
"The Zimbabwean situation is now a complete humanitarian outrage, compounded by self-serving and self-deceiving pronouncements from those clinging to power," he said.
Three rights groups, Amnesty International, Human Rights Watch and the Open Society Institute, also joined forces on Wednesday to demand an end to abductions in Zimbabwe and the immediate release of four missing activists.
In a statement the organisations warned that the abduction of three members of the Zimbabwe Peace Project (ZPP) and the brother of a human rights lawyer "may constitute an enforced disappearance which is a serious violation of international law".
ZPP director Jestina Mukoko was taken from her home in Harare in the early hours of December 3 by a group of armed men, who identified themselves as police.
Two other ZPP employees were snatched from their offices on Monday, while the brother of a Mukoko’s lawyer was nabbed at his home in the southern town of Masvingo last weekend.
A High Court judge on Tuesday ordered police to search their jurisdictions for Mukoko, despite the police claiming to have no knowledge of her whereabouts.
A group of 15 MDC members that were detained by police in early November are also missing.
The new security crackdown comes as the official death toll in a raging cholera outbreak shot up to 746 from 589 a few days ago and the total number of suspected cases raced ahead to 15 572, the UN Office for the Coordination of Humanitarian Affairs said.
The sudden spike may be due to the fact that the UN is now obtaining statistics on people who died in their communities, outside of health facilities.
On Tuesday, Information Minister Sikhanyiso Ndlovu accused Western powers of contaminating Zimbabwe with cholera to justify military intervention and accused opposition leader Morgan Tsvangirai of denying Zimbabweans relief by refusing Mugabe’s terms for joining a unity government.
Tsvangirai and Mugabe disagree on how to implement the power-sharing deal to which they agreed in September.
In a BBC interview Wednesday Tsvangirai placed the blame firmly for the economic and humanitarian crisis at Mugabe’s feet.
"Mr Mugabe must realize he is responsible for the current crisis," he said, emphasizing that further negotiations were needed to hammer before an inclusive government could be formed.
Among the sticking points in the deal, which sees Mugabe remain president and Tsvangirai become prime minister, are the sharing of key cabinet posts between their parties, particularly the home affairs ministry.
The MDC says it should run that ministry given the history of state violence against its members. Mugabe’s Zanu-PF is insisting on shared control. – Sapa-dpa