By Will Ross
BBC News, Kampala
Police in Uganda have used water cannon, tear gas and pepper spray to break up an opposition rally.
Demonstrators were allowed to march last week
It was called to protest against efforts to amend the constitution and allow President Yoweri Museveni to stand for re-election next year.
Last week there were two demonstrations in the capital, Kampala - one in favour and one against Mr Museveni running again - but this rally was banned.
Party politics has been restricted for years to reduce sectarian violence.
Police say 17 people have been arrested for taking part in the demonstration. The organisers, including the FDC's David Pulkol, were questioned at a police station but the police deny that they too have been arrested.
The police granted permission for both last week's demonstrations to take place and many viewed the events as a sign of greater democracy and freedom of speech in Uganda.
The violent dispersal of this latest demonstration may change that feeling but it is still likely to play into the hands of the pro-Museveni government.
The protestors are liable to be blamed for defying police orders.
If further rallies are banned, many people will be deterred from attending and the anti-President Museveni voices will effectively be muted.
Mr Museveni, who came to power in 1986, is due under the constitution to step down in a year's time after serving two terms in office.