North Korea has sent a fax to South Korea threatening to “strike mercilessly without notice” after protests against the secretive regime. The message warned that North Korea would strike if “the provocation against our highest dignity is to be repeated in the downtown of Seoul.” The fax addresses protests earlier this week in which conservative protesters rallied in Seoul, burning effigies of the country’s leaders as well as its flag during an anti-North Korean rally on the second death anniversary of former leader Kim Jong Il. …