Among those detained are a journalist, three lawyers, an academic and a union representative, according to local media and a human rights group.
Turkey is planning strict security measures for the summit. Among other measures, it was announced on Monday that all demonstrations will be banned from June 28 until the summit, which will be held on July 7-8.
Of those arrested, 185 are accused of membership in various left-wing organizations, including the extremist DHKP-C, which has previously claimed responsibility for attacks in Turkey. Others are suspected of links to IS.
On Tuesday, Turkish prosecutors ordered the arrests of 241 suspects.
What do you think?