Several people were detained on Monday, 21 were injured in clashes and several people fainted in the crush. Police said there had been 90 arrests related to the protests in Edinburgh.
The demonstrations began peacefully as protesters, banging drums and shaking bells, marched and danced into waiting police containment cordons.
The demonstrations were part of an array of protests that began on Saturday with a 200,000-strong march through the city calling for an end to poverty in the developing world, especially Africa.
Leaders of the Group of Eight industrialised nations meet amid tight security from Wednesday to Friday at Scotland's Gleneagles Hotel, tasked with tackling African poverty and devising a strategy against global warming.
On Monday, black-clad and masked members of the Black Bloc, an anarchist group based in Germany and Scandinavia that has been prominent in protests at past G8 summits, mingled with other demonstrators dressed as fairies and clowns.
Protests have been under way
since Saturday in Edinburgh
Trouble began when about 30 anarchists, among about 200 protesters trapped between lines of police, pushed and scuffled with police officers.
In one incident, 14 mounted riot police and 15 vanloads of others arrived to protect the Standard Life insurance company building to find just three demonstrators there.
Mindful of the violence that erupted at previous G8 summits in Genoa, Italy, in 2001 and Evian, France, in 2003, Scottish police have been taking no chances.
Around the city, mounted riot police and convoys of police vans with sirens wailing and lights flashing sought to curtail anarchist street demonstrations.
Tourists appeared to be enjoying the spectacle. "This is entertaining and at least it is cheaper than paying to go and visit the castle," said Ricky from Hong Kong.
A police spokesman said late on Monday that 21 people, including four police officers, were injured but none seriously. Most of the charges relating to the 90 arrests were for causing a disturbance.
The spokesman said Edinburgh was quiet late on Monday night but added: "It could be lively on Wednesday."