Yemeni officials say at least 51 people were crushed to death and more than 200 wounded in a stampede at an election rally for President Ali Abdullah Saleh.
Witnesses say the stampede began Tuesday after the president finished speaking at a stadium in the southern province of Ibb.
Reporters say more than 100,000 people had gathered inside the stadium and a larger number were on the streets around the building.
Yemen is to hold presidential and local council elections next week September 20.
Separately, Yemeni tribesmen holding four French tourists hostage have threatened to kill them if authorities use force to try and free them. Tribal sources issued the threat after talks with authorities failed.
Yemeni authorities have said tribal officials are seeking the release of several relatives from prisons in Yemen.
Tribesmen kidnapped the tourists Sunday in Shabwa province in eastern Yemen.
Some information for this report provided by Reuters, AFP and AP.