ATHENS — After a violent clash between Greeks and migrants seeking asylum in Europe, the Greek authorities and human rights groups say they fear rising tensions and more conflicts on the eastern Aegean Islands that house tens of thousands of refugees who have arrived via Turkey.

The confrontation, which lasted for hours on Sunday and Monday, took place on the island of Lesbos, where tolerance of the growing refugee population has worn thin, and where members of far-right, anti-immigrant groups have been exploiting the frustration. Tensions in the overcrowded migrant camps often erupt into brawls and riots, but major clashes with Greeks have been rare since the flood of refugees from Asia and Africa began three years ago.

About 200 Afghans had been camped for several days in a central square of Mytilene, the main port city of Lesbos, to protest living conditions in the government-run camps and delays in processing their asylum applications. Lesbos is one of the areas most burdened by the refugee crisis; about 8,700 of the 60,000 migrants living in Greek camps are housed there.

On Sunday, local residents gathered in Mytilene to object to the presence of the Afghans, a demonstration that escalated into violence. Some of the protesters pelted the migrants in the square with flares, firecrackers and stones broken off sidewalks, and some chanted “burn them alive,” according to local news media.