Lusaka - Zambia's biggest independent newspaper has been shut down by authorities over unpaid taxes, the editor said on Wednesday, calling the move an attempt to silence it ahead of August elections.Police and tax officials physically closed the Post newspaper's offices in Lusaka late on Tuesday, managing editor Joseph Mwenda told AFP, leaving staff gathered outside the locked building on Wednesday.Mwenda said staff had managed to produce the daily paper overnight with the help of a private printing company.The Post admits owing about 53 million kwacha ($4.8m) in unpaid taxes, but Mwenda said the closure of the paper was illegal."This is a clear abuse of power because we have paid some money and we even have a court order stopping them from going ahead but they have disobeyed the courts," he said."It's clear that they want us shut down ahead of the elections."General elections are due on August 11.The Post, which was established in 1991, has been critical of President Edgar Lungu, who is seeking re-election.Amnesty International said the publication was "one of Zambia's few politically outspoken and critically independent newspapers"."The closure of The Post newspaper is a disturbing development clearly designed to silence critical media voices," it added.