MYANMAR’S ruling military junta warned on Friday that pro-democracy protesters risked being shot in the head or back as activists called for a huge show of defiance against the generals on the country's Armed Forces Day on Saturday. Troops killed four more people in demonstrations on Friday, adding to a reported death toll of more than 320 people in the crackdown that has followed the coup against Aung San Suu Kyi's elected government on February 1. A broadcast on the state MRTV news channel said: "You should learn from the tragedy of earlier ugly deaths that you can be in…