TULSA: Tulsa, Oklahoma has imposed a curfew ahead of a campaign rally by US President Donald Trump on Saturday, amid tensions in a city that was the site of one of the worst racial massacres in US history.

In an executive order Thursday, Mayor G.T. Bynum cited fears of violent protests surrounding Monday's rally in proclaiming a "civil emergency."

The curfew, which went into effect at 10 pm Thursday until 6 am Saturday and resumes after the rally until 6 am Sunday, covers an area in downtown Tulsa around the arena where Trump is to speak.

More than 100,000 people were expected to attend the rally, which has been sharply criticized as both a potential COVID-19 superspreader event and insensitive to Tulsa's painful racial history.

In May and June of 1921, a white mob burned down a black Tulsa neighborhood, Greenwood, killing as many as 300 people and destroying some 1,200 buildings.