SAN`A, Yemen (AP) – A stampede during a campaign rally Tuesday for President Saleh killed at least 41 people and injured more than 50 _ most of them schoolchildren and teenagers, medical and security officials said.

The stampede occurred in a small stadium in Ibb, 119 miles south of the capital San`a, where Mr. Saleh was addressing a group of people.

Officials at Thawra Hospital said 20 bodies were brought there. At Al-Nasser hospital, officials revised their death toll to 21 from 12 after some of the people taken there died from their injuries.

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

Overcrowding and a lack of clearly marked exits contributed to the stampede, as people leaving the stadium ran into others entering it, the officials said.

Mr. Saleh offered condolences to the families of the victims, as did opposition groups, who called for a full-scale investigation and urged the government to punish those responsible.

The teenagers and schoolchildren had been bused to the stadium by government authorities to attend the rally.

The election is scheduled for Sept. 20.