At least 166 undocumented migrants have been held in Istanbul and southern Turkey, security sources said on Wednesday.

In Turkey's largest city, Istanbul, 115 Pakistani nationals were held in the Çatalca district after Turkish security forces were tipped off that the group was planning cross into Greece via Edirne, western Turkey, the source, who spoke on condition of anonymity, said.

Police stopped four minibuses at different times and held undocumented migrants who reportedly came to Turkey via Iran and had been staying in Istanbul's central Aksaray district for around a month, the source added.

Six Turkish nationals and a 17-year-old Pakistani have been arrested over reportedly being organizers of the voyage and taking $1,500 from each migrant. The suspects were later remanded in custody by a court, the source added.

In Istanbul's Silivri district, 34 Syrian nationals, mainly women and children, were also held, the source said. One suspect was arrested, the source added.

Earlier today, in Turkey's southern province of Hatay, 17 undocumented migrants were held, the security source said. The migrants were found after they crossed into Hatay's Yayladağı district from Syria.

All the migrants were Syrian nationals, according to the source.

Turkey has been the main route for migrants trying to cross into Europe, especially since the beginning of the civil war in Syria.