Mevani, who has been spearheading the agitation triggered by the Una flogging incident, was reportedly arrested as a preventive measure.
Fearing that he might create some problem at felicitation event organized for Modi near airport he was detained.
Hours before, in Delhi, Mevani had announced that a rail-roko agitation would be launched from October 1 in Gujarat, if the government did not comply with their demand for a 5-acre land to be alloted to every dalit family in the state.
Dalits had made this demand at the flag-hoisting ceremony in Una on August 15 at the end of a 10-day march against the alleged atrocities against the group.
Around 400 Patidars were also detained on Friday to prevent any type of problems.