But the rally was cut short when a group of about 50 Orthodox Christian counter-demonstrators, singing and reciting prayers, attacked the activists, said an AFP photographer.
Police broke up the fight and arrested activists from both sides, about 20 people in all.
Gay rights is a divisive issue in Russia, where homosexuality was considered a crime until 1993 and a mental illness until 1999.
In June, President Vladimir Putin signed a controversial new law against "gay propaganda" that has drawn international condemnation and calls to boycott the 2014 Winter Olympic Games in Sochi in southwestern Russia.
Source: AFP