French riot police briefly used water cannons and tear gas on Saturday to disperse protesters in Bayonne, near the resort of Biarritz where President Emmanuel Macron and G7 nation allies were meeting for a three-day summit.
A police helicopter circled overhead as dozens of protesters, some wearing face masks, taunted lines of police.
Some threw stones and other objects at the police and kicked back tear gas cannisters. Several people were seen to be detained.
Earlier, thousands of anti-globalisation activists, Basque separatists and "yellow vest" protesters marched peacefully across France's border with Spain to demand action from G7 leaders.
More than 13,000 police officers are guarding the summit site in Biarritz under fears that anarchist groups might have tried to derail Saturday's protest, which has been billed as a peaceful family event.
Four police officers were lightly wounded on Friday after protesters fired a home-made mortar near the anti-G7 counter-summit in Hendaye. Police arrested 17 people for hiding their faces.
On Sunday, activists plan "disobedience" actions and the self-described radical environmentalist group "Action non-violente COP21" will defy a ban on demonstrations in Bayonne, with a march carrying official portraits of French President Emmanuel Macron which it says have been taken from town halls around the country.