A panicked crowd at a political rally in southern Nigeria trampled at least 11 people to death and injured dozens more as President Goodluck Jonathan gave a speech promising to change Africa's most populous nation for the better, authorities said on Sunday.

The stampede at the rally in Port Harcourt was to serve as a homecoming for a leader born in the oil-rich region. Instead, the rally highlighted the country's volatility ahead of April's national elections, and Jonathan's convoy caused a fatal traffic crash even before the stadium melee.

Organizers held the rally Saturday at Port Harcourt Liberation Stadium, a soccer venue that can hold about 25,000 people. As Jonathan began his speech, some attendees began to try to leave to beat the traffic out of the stadium, while others pushed their way inside to hear his speech, said Ibim Semenitari, a Rivers state government spokeswoman.

Eleven people died in the crush, Rivers state police spokeswoman Rita Inoma-Abbey said. Semenitari said at least 46 others had sought treatment at hospitals.

Jonathan was not injured during the stampede and his office issued a statement about the "unfortunate loss of lives" at the rally before local officials confirmed any fatalities.

"I am sad and heavily weighed down by this incident," the statement quoted Jonathan as saying. "It is sad, unfortunate and regrettable. I mourn with those who mourn tonight. May God grant us all the fortitude to bear this irreparable loss."

Inoma-Abbey said authorities had set up an investigative panel to look at the cause of the stampede. Such stampedes remain a danger at large events in Nigeria, where police often have no formal training handling large crowds.

Political parties often pay the unemployed to attend such events to swell numbers, while organizers often hand out free hats and shirts to attendees — a valued gift in a country where most earn less than $2 a day.

Stampedes are "usually a thing that happens at a rally," Semenitari said.

Even before the event, Jonathan's visit was marred by deaths. As his large presidential convoy moved through the two-lane roads outside of Port Harcourt, one vehicle crashed into a civilian automobile. Local newspapers reported at least two people died instantly in the crash, though authorities would not confirm that Sunday.