Senior pro-independence leader and chairman of the Jammu and Kashmir Liberation Front (JKLF) Muhammad Yasin Malik and twelve of his party colleagues were taken into preventive custody on the outskirts of the city on Friday.
The authorities said Malik was held to prevent him from disturbing law and order.
A JKLF spokesman said Malik was to address a public gathering at Bandipora, 55 km north of the capital after Friday prayers.
They were detained at Maloora, 44km away from the destination, and lodged in the Parimpora police station.
The separatist leader has been asking people to boycott the forthcoming parliamentary and assembly elections for the past few weeks.
Meanwhile, hardline Hurriyat Conference leader Syed Ali Shah Geelani was barred from offering prayers for the 36th Friday, said Ayaz Akbar, spokesman of the organisation.