Supporters of Jordan's government have attacked pro-reform protesters to stop them from gathering in a main square in the capital.
Police wielding clubs quickly got involved, beating the anti-government protesters and journalists, wounding at least 10 people.
The crowds had been trying to gather Friday to call for political reforms.
Jordanians have held six months of protests inspired by the revolutions in Egypt and Tunisia to demand a greater political voice.
Last month, King Abdullah II endorsed a key demand to have prime ministers and Cabinets elected from parliamentary majorities, but he later said it may take two to three years to put an elected government in place rather than one appointed by the monarch.