Akhir 20, 1432, March 25, 2011, SPA -- A Zimbabwean cabinet minister was arrested on corruption charges on Friday, the latest sign of tensions between President Robert Mugabe and rival Prime Minister Morgan Tsvangirai's party ahead of possible elections, according to Reuters. Mugabe's ZANU-PF party and Tsvangirai's Movement for Democratic Change (MDC) are supposed to be partners in a unity government that is coming apart at the seams. The MDC said Energy and Power Development Minister Elton Mangoma, who was on bail on a graft charge over a fuel import deal, was arrested on Friday for the second time in two weeks. Mangoma, a Tsvangirai ally and deputy treasurer of the MDC, is accused of forcing officials to cancel a tender contract for a power supply pre-payment system. Mangoma's lawyer Selby Hwacha said the minister would plead not guilty. "As far as we are concerned this is part of a harassment campaign that ZANU-PF has embarked on against our structures, and it is the type of campaign that we have suffered before every general election," an MDC official told Reuters. Tsvangirai urged regional leaders last week to intervene to save Zimbabwe's unity government from threats posed by a spate of political violence against MDC supporters. Tsvangirai and Mugabe were forced into a coalition two years ago after a disputed poll in 2008, which led to mass violence and a flood of refugees into neighbouring South Africa. Relations between the coalition rivals have worsened in the past two weeks since police first arrested Mangoma and the Supreme Court nullified the election of another Tsvangirai ally as Speaker of Parliament. Police have also arrested dozens of activists accused of plotting protests against Mugabe similar to those that toppled long-serving leaders in Egypt and Tunisia. Critics say Mugabe, 87 and in power since independence in 1980, has used brutal policing and vote rigging to keep his grip on power despite a deep economic crisis. Mugabe denies the charges, and accuses Western media of waging a hate campaign against him over his seizures of white-owned farms for redistribution to black Zimbabweans.