Thousands of Zimbabwean opposition supporters took to the streets on Tuesday to call for electoral reforms to prevent fraud and voter intimidation ahead of presidential elections on July 30.Brandishing placards, singing and dancing, noisy activists defied the cold and marched with the main Movement for Democratic Change (MDC) to the country's electoral commission in Harare, halting traffic and drawing onlookers."We will not allow an election which is not free and fair," MDC leader Nelson Chamisa told supporters after handing over a petition to the commission. "We are prepared to do anything necessary. We will keep pressuring them. We will do this every day until we get the reforms we want." The opposition are demanding the publication of the full voter roll, independent audits of ballot papers as well as guarantees of safety for non-government candidates. "Why are you deploying soldiers against a political party?" Chamisa asked the crowds which marched watched by a heavy security presence.Opposition parties are also calling for military personnel seconded to the commission to be removed. * Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and FacebookZimbabwe's next polls will be the first since the fall of long-time ruler Robert Mugabe who was forced to step down following a brief military takeover in November.Mugabe who had been in power since Zimbabwe's independence from British colonial rule in 1980 was replaced by his former deputy, President Emmerson Mnangagwa.Previous elections in Zimbabwe were marred by violence which peaked in 2008 when then-opposition leader Morgan Tsvangirai boycotted a presidential run-off because of a spate of deadly attacks on his supporters. Mnangagwa has pledged "free, fair and credible elections" as he seeks to end Zimbabwe's isolation and mend fences with the West.He will face-off against Chamisa who became leader of the MDC following Tsvangirai's death from colon cancer in February. The ruling ZanuPF party's youth wing is planning street marches on Wednesday in support of the government and Mnangagwa.