Rioters took to the streets of the two main towns in Zambia's Copper Belt on Thursday amid frustration at a delay in tallying the results of this week's presidential election in Africa's biggest copper producer, police said.

They are on the streets with stones and we can only urge them to stop the riotous behavior, Copper Belt police chief Martin Malama said.

We have not assessed the extent of the damage yet because we are still trying to contain the situation.

(Reporting by Chris Mfula; Editing by Ed Cropley)