The arrests were made after the Punjab government led by Chief Minister Shahbaz Sharif refused to allow the Council to hold the public meeting at the monument for "security reasons".
Council chairman Sahibzada Fazal Karim, however, asked activists to reach the venue at any cost and to stage sit-ins wherever they were stopped by police.
Another Sunni Ittehad Council leader Muhammad Nawaz Kharal said the group's central vice chairman Muhammad Afzal Qadri and five top leaders of different Sunni organizations had been taken into custody by police at the Minar-e-Pakistan, where they had gathered to oversee arrangements for the proposed meeting.
"Not less than 600 activists, including 200 from Minar-e-Pakistan, have been captured by police," Kharal claimed.
He said he feared more arrests would be made as motorcades of activists from across the country were reaching Lahore to take part in the meet.
A senior police officer said the organizers of the meeting had earlier reached an understanding with the local administration that they would hold the "Istehkam-e-Pakistan" (Stable Pakistan) conference at Attique Stadium near Lahore Fort but they "backed out at the last minute".
Lahore police chief Muhammad Aslam Tareen said nobody would be allowed to gather at the Minar-e-Pakistan following the government's orders.