San’a, Yemen ? A stampede broke out Tuesday in a stadium packed with thousands of people for an election campaign rally for Yemen’s president, killing at least 51 people and injuring more than 200, including youths bused in for the event.

The tragedy came as President Ali Abdullah Saleh — in power for nearly 30 years — is campaigning in the oil-rich nation’s first competitive presidential elections, set for Sept. 20, against a single rival who has drawn tens of thousands to his rallies.

The president has been eager to show he has broad popular support — even announcing last year that he would not run for re-election, then reversing himself, citing appeals from the public for him to stay.

Saleh, who has allied himself with the U.S. in the war on terror, offered condolences to the families of the victims of the stampede, which occurred at a rally where he was speaking to the town of Ibb, 120 miles south of the capital, San’a.

The stadium was filled beyond its capacity of around 10,000. Government workers and students from schools around the Ibb area had been brought in on government buses to participate.