Several hundred people attended the event during which a masked man read out a statement from the Real IRA, threatening to attack police.
The arrested men were taken to Antrim police station for questioning.
The police said they kept a distance from the rally, but a security force helicopter monitored the scene.
The BBC's Ireland correspondent Mark Simpson said a small group of men lined up and marched in paramilitary style uniforms during the event, which was held at Creggan Cemetery in the city.
...