Image of tear gas
Reports say a presidential candidate and the head of an opposition party are among several people injured, after security officers fired tear gas on people at a rally in Madagascar's capital Antananarivo.
However, neither of them have been named.
Two bodyguards protecting ex-President Marc Ravalomanana - who's running for re-election - were arrested.
"We did not succeed today," said Jean Jacques Ratsietison, another candidate, telling the broadcaster RFI that "we will come back tomorrow, the day after tomorrow, until we reach an agreement between all parties".
Eleven of the 13 presidential candidates are asking their supporters to protest against what they described as an "institutional" coup in favour of the incumbent, President Andry Rajoelina.
They say they fear next month's election will not be free and fair and have accused the electoral commission of favouring Mr Rajoelina.
The electoral commission has not commented on the allegation
