Police in Zimbabwe's second city, Bulawayo, have blocked a political rally. It was to have been addressed by Morgan Tsvangirai, leader of the opposition Movement for Democratic Change. The opposition says 18 people were hurt by tear gas and police beatings.

The rally was the first to be held by the Movement for Democratic Change in Bulawayo since it was announced last week that presidential elections will be held March 9 and 10.

The opposition party says trouble began Saturday evening when supporters of the ruling ZANU-PF party scuffled with MDC security guards at the soccer stadium where the rally was to be held.

The MDC says that early Sunday police stopped vehicles from heading towards the stadium and later used teargas to drive away people who were walking to the rally. Mr. Tsvangriai, who opposes President Robert Mugabe in the forthcoming election, canceled his appearance as trouble worsened.

Later, MDC Secretary General Welshman Ncube accused the police of acting in collaboration with President Mugabe's ZANU-PF party to stop the rally. He pointed out that it was only last week that Mr. Mugabe pledged at a meeting of southern African heads of state in Malawi that the Zimbabwe elections would be free and fair.

Bulawayo is a stronghold of the MDC. The party won all the city's parliamentary seats in national elections last year.

Meanwhile, Nigerian president Olusegun Obasanjo flew to Harare for talks with Mr. Mugabe about Zimbabwe's political and economic crisis.