Prime Minister Vincent Siew Wan-chang last night called for calm in the elections after 10 days of campaigning marked by violence, mudslinging and vote-buying allegations. 'The public should join efforts to fight violence and vote-buying to improve the quality of elections and ensure an open and fair race,' Mr Siew said. Authorities have pledged to crack down on violence, fraud and irregularities in the polls. Provincial police yesterday said they had received requests for riot police to be stationed in 16 cities and counties across the island, starting this afternoon. Wang Yi-fei, director of the provincial police, said officers were expecting at least 10 of the 16 polling areas to be potential trouble spots. They include Taipei county, the island's most populous, as well as southern Yunlin county, where prosecutors have warned of 'intrusion' by gangsters. More than 800 riot police would be assembled and placed on call in Taipei county, he said. This week, the State Public Prosecutor's Office said it had evidence that gangsters were forcing an unknown number of Yunlin residents to hand over or sell their identity cards. Prosecutors, who declined to say which candidate the gangsters were working for, said they suspected voters were being told they could get their ID cards back after voting for the candidate favoured by the gangs. Meanwhile, local prosecutors' offices island-wide were busy collecting evidence of alleged vote-buying and other irregularities. By yesterday afternoon, they were working on a total of 483 reported cases, ranging from allegations of offering cash for votes to violence and threats against voters, campaign aides or candidates. Police said 72 officers had been assigned as extra bodyguards for 33 candidates. The majority of reported cases involved allegations of vote-buying, the State Public Prosecutor's Office said. A total of 851 people were being questioned in connection with the allegations. Votes were said to be selling for anywhere between NT$500 (HK$118) and NT$2,000. But there was nothing to stop voters taking money from one candidate but casting a ballot for another, since voting was secret, the prosecutor's office added. Six cases of violence considered 'serious' were being investigated, including cases of gangsters shooting at empty campaign offices.