AFP, Hong Kong :Hong Kong democracy activists on Tuesday marked one month of mass protests, calling on supporters to gather for an evening rally wearing the masks they have used to ward off police tear gas and pepper spray.Organisers striving to inject new momentum into the movement told crowds to gather at the main protest camp opposite the city’s government headquarters for commemorations starting with an 87-second silence at 0957 GMT.At that time on September 28, riot police shot 87 volleys of tear gas at crowds of largely peaceful protesters who had taken over a highway near the city parliament.That decision backfired, drawing tens of thousands of sympathisers onto the streets and kickstarting a movement that has become the most concerted challenge to Beijing since the bloody 1989 Tiananmen protests.