Authorities were checking the identities of those contained and some could face arrest and prosecution, Laurent Paoliello, a spokesman for local authorities, told Swiss broadcaster RTS on Sunday.
Paoliello said property damage was limited and praised the police operation. No injuries were reported.
Thousands of demonstrators have gathered in Geneva to protest against the G7 summit, which is due to begin on Monday in the French lakeside town of Évian, 50km across the border from Switzerland.
The peaceful march was overshadowed by a hard core of masked protesters who tore up paving stones and smashed several shop windows. Police responded with tear gas and later deployed water cannon to disperse the unrest.
Police estimated that around 20,000 people took part in the demonstration, while organisers put attendance at 60,000. Around 7000 security personnel were deployed.
The masked protesters also set a car and rubbish bins on fire, and smashed numerous windows - of shops, bus stops, advertising hoardings and the entrances of UN organisations.
Police kept a low profile for much of the day, but away from the approved march route they cordoned off the main bridge over the Rhône leading to the main shopping streets and, elsewhere, the United Nations headquarters in the Swiss border city just along the shores of Lake Geneva from the G7 summit venue.
Police said on Facebook that they had confiscated several objects that appeared to have been intended for use in confrontations with officers.
According to its manifesto, the No G7 coalition of 60 organisations demonstrated against US military bases in Europe and in favour of higher minimum wages, free contraception, unrestricted freedom of movement for workers from around the world and the removal of gender from all identity documents.
The coalition described the G7 as an "illegitimate and outdated institution, a private club that no longer reflects today's world," where "major powers make decisions in favour of the most privileged minority in the world and to the detriment of more than 90 per cent of the population."
The summit of G7 leaders from Germany, France, the United Kingdom, Italy, Canada, Japan and the US begins on Monday.
France was unwilling to allow protests near the summit zone, according to the Geneva city government. Organisers therefore registered the demonstration in Geneva.
