The state-run Anadolu Agency said police in the Mediterranean coastal city of Antalya on Sunday blocked the four protesters from marching toward the secluded seaside resort of Belek, where the leaders are meeting.
The group then held a sit-down demonstration before being detained and taken to a sports center which has been turned into a temporary detention center for protesters during the summit meeting, the agency reported.
The leaders of the world's 20 top economies are meeting for a summit that is expected to be dominated by the fight against extremists following the Paris attacks.
At least 129 people were killed in Paris on Friday by gunmen and suicide bombers in attacks claimed by ISIL terrorists.
A state of emergency has been declared in the European country shaken by the horrific attacks.