Zimbabwean officials deported Nowak on Thursday after he was detained by security officials on arrival overnight
Nowak, the UNHRC’ special rapporteur on torture and other cruel, inhuman or degrading treatment, told reporters after arriving in South Africa that his mission had failed.
"I think that it is the end of the mission. I think I have not been treated by any government in such a rude manner than by the government of Zimbabwe. I will not (go) back," Nowak said.
Nowak said he remained concerned about torture in Zimbabwe and would recommend that the UNHRC take action against the country.
"I will report to the Human Rights Council and I will recommend to them to take necessary action in respect of Zimbabwe."
Nowak did not say what action the council might take against Zimbabwe.
He said he had been invited to Zimbabwe by Prime Minister Morgan Tsvangirai, whose power-sharing deal with President Robert Mugabe is under severe strain.
"I think it sheds light on the present power structure of the unity government if the prime minister invites me for a personal meeting and his office is not in a position to clear my entrance to the country. That is a very alarming signal about the power structure of the present government."
Tsvangirai’s Movement for Democratic Change (MDC) has stopped cooperation with Mugabe’s ZANU-PF in the unity government.
On Wednesday night a Reuters reporter saw Nowak being approached by four security officials at Harare airport after he had cleared immigration.
Zimbabwe’s state-owned Herald newspaper accused Nowak of trying to "gatecrash into the country".
The newspaper said Nowak had been informed by the government that he could not visit because the country was hosting foreign ministers from the Southern African Development Community.
"Government had already communicated to him that he would have to visit on a later date," the Herald said.
Officials from SADC, a regional grouping, opened talks on Thursday with the rival Zimbabwean parties in a bid to patch up the rift threatening the power-sharing government.
"The SADC delegation has already started the engagement process, with the ministers and officials talking to the different parties, laying the groundwork for consultations with the principal leaders," one SADC official told Reuters.
"We are not going to be playing this in the gallery because that is not constructive or the way to conduct a review or to mediate in any dispute," said the official who declined to be named or to discuss his team’s chances of success.
Mugabe, who has led Zimbabwe since independence in 1980, formed a power-sharing government with Tsvangirai to end months of feuding in the impoverished country.
But Tsvangirai said two weeks ago he was boycotting the arrangement until problems had been resolved.
Nowak’s invitation marked the first time Zimbabwe had offered to open up to an expert working for the U.N. Human Rights Council.
The urgency of an objective fact-finding by an independent U.N. expert was highlighted by allegations of the arrest, intimidation and harassment of MDC supporters and of human rights defenders in the past few days, the U.N. said.