39 DIE IN MOSCOW AS BOMB GOES OFF ON SUBWAY TRAIN
Bomb explodes inside Moscow subway train during morning rush on Feb 6, killing at least 39 people and wounding over 130; no one claims responsibility for bombing though senior government officials, including Pres Vladimir V Putin, suspect that it is latest in series of terrorist attacks linked to war in Chechnya; hundreds of passengers have to stagger through smoke-filled tunnels to reach safety; Putin blames wave of terror on separatist leader Aslan Maskhadov; map; photos (M)