Sanaa: More than 40 people were killed and at least 150 were injured during a pre-election campaign for President Ali Abdullah Saleh in the southern province of Ibb on Tuesday.

The incident occurred after part of the Ibb stadium, 200 kilometres south of the capital Sanaa where the poll rally was held, collapsed on the people while they were getting out after the rally, witnesses told Gulf News.

The resulting chaos led to a stampede, they added.

"Medics and policemen moved about 100 injured people to hospitals," said one of the witnesses.

"The collapse of part of the stadium would not have killed and injured this many people, if they had stopped running out," said the witness.

Saleh, the ruling party candidate for the presidential elections to be held on September 20, immediately sent condolences to the families of the victims describing them as "the democracy martyrs".

Ibb is one of the most populated provinces in Yemen. The opposition, meanwhile, issued a statement blaming the authorities for the incident, saying that the stadium, which was opened on Monday, has a problem "with the concrete specifications".

Yemen is witnessing a hot election campaign over the presidential office.

Four candidates, the most prominent of whom is the opposition alliance candidate Faisal Bin Shamlan, are vying with the incumbent president Saleh.