South African President Thabo Mbeki intervened with the Zimbabwean government on behalf of opposition leader Morgan Tsvangirai "immediately" after hearing of his detention Wednesday, Mbeki's office said Thursday, according to dpa. "Upon being informed by the MDC of the arrest of its leader, Mr Morgan Tsvangarai, in Lupane, Zimbabwe yesterday, SADC (Southern African Development Community) Facilitator, President Thabo Mbeki, immediately contacted the government of the Republic of Zimbabwe to ascertain the circumstances of the arrest," the statement said. Tsvangirai's nearly day-long detention while campaigning in western Zimbabwe sparked outrage internationally, with the United States, Britain, Germany and the European Union all calling for his release. Police said he was held over irregularities in the papers of his vehicle. Mbeki was appointed by the 14-nation SADC as mediator in Zimbabwe last year but his reticence on human rights abuses in the country have led Zimbabwe's opposition to accuse him of bias towards President Robert Mugabe and call for his removal. South Africa's Sunday Times and Citizen newspapers over the past week printed excerpts from a letter allegedly sent by Tsvangirai to Mbeki telling him: "If you go on like this, there will be no country left." Mbeki's spokesman has denied he ever received any such letter. The presidency said Thursday that Mbeki had "urged the (Zimbabwean) government to do everything possible to ensure that every party involved in the forthcoming presidential run-off does so in conditions that are free and fair."