Police detained four protesters who wanted to deliver a letter to the leaders.
A group of some 500 youths belonging to a Turkish nationalist association marched in Antalya, holding up effigies of US President Barack Obama and denouncing US interventions in the Middle East.
Hundreds of members of Turkish left-wing groups and trade unions later held another protest denouncing the organisation which gathers the world's wealthiest economies.
They marched in central Antalya carrying a banner that read in Turkish and in English: "Killer, colonialist, imperialist war organisation G-20 get out!"
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All of the protests took place some 40 kilometres away from the summit venue under heavy riot police presence.
Earlier, police detained four protesters who wanted to walk to the venue of the G-20 summit to deliver a letter to participants.
The state-run Anadolu Agency said police blocked the four protesters from marching toward the venue, prompting them to hold a sit-down demonstration.
Police detained the group and took them to a sports centre that has been turned into a temporary detention centre for protesters, the agency reported.