At least 41 people were killed and dozens 70 injured Tuesday in a stampede during a campaign rally for the president, medical and security officials said. Most of the victims were schoolchildren and teenagers.

The stampede occurred in a small stadium in the southern province of Ibb, where President Ali Abdullah Saleh was making a campaign speech, security officials said.

Overcrowding and a lack of clearly marked exit signs contributed to the stampede, according to the officials, who said that people trying to leave the stadium ran into people trying to enter.

Some of the injured were in serious condition, the medical officials in Ibb said on condition of anonymity because they were not authorized to speak to the media. Five of the injured were treated and released.

CountryWatch: Yemen

The youths had been bused to the stadium by the government.

Saleh faces a former oil industry executive picked by the five main opposition parties.

The president, who has been in power 28 years, provoked criticism when he reversed a pledge not to seek another seven-year term. The election is scheduled for Sept. 20.

Yemen was the scene of the 2000 bombing of the destroyer USS Cole, which killed 17 American sailors. After the Sept. 11, 2001, attacks, the country allied itself with the U.S. war on terrorism and cracked down on militants.