Police say Thursday's riot in the central town of Garissa began when supporters of the referendum tried to disrupt a rally held by opponents of the constitution.

Police restored order after the crowd hurled rocks, bananas - the ballot symbol for a "yes" vote - and oranges, representing a "no" vote.  At least one person was injured.

Kenyans are to vote on a new proposed constitution in a national referendum on November 21.

The 197-page document allows Kenyan President Mwai Kibaki to retain his wide-ranging powers.  Opponents say it fails to establish a strong prime ministerial post, which they argue is needed to balance the president's authority.