Myanmar launched three days of official mourning at 9:00am (0230 GMT) Tuesday for more than 133,000 people left dead or missing by Cyclone Nargis, lowering national flags to half mast. The mourning period is one of the first demonstrations of public grief since the tropical storm ravaged swathes of this impoverished nation 18 days ago, leaving about 2.4 million survivors desperately in need of aid. Flags in front of Yangon's City Hall fluttered at half mast in the light morning rain, but there was no minute of silence or a public ceremony, leaving many people unsure how to mark the solemn occasion.