"A total of 136 people were detained for various offences during an uncoordinated rally in the centre of Moscow", the police said.
Earlier, the Moscow government agreed two rallies on 10 and 11 August on Academician Sakharov Avenue, up to 100,000 participants each. According to police figures, about 20,000 people attended the rally, while the event's organisers claim attendance of 50,000. The events' organisers subsequently cancelled Sunday's rally.
The protests have been going on since mid-July in the Russian capital. They were called by opposition figures who were denied registration for the elections to the Moscow city council scheduled for 8 September.
The previous rallies were not authorised by the Moscow authorities. The protests resulted in the detentions of hundreds of protesters. Most of them were released later. Some of the organisers of the protest were arrested until late September.