Yasin Malik has been arrested many times before
Police in Indian-administered Kashmir have arrested senior separatist leaders who are urging a boycott of next month's state assembly elections.
The chief of the Jammu Kashmir Liberation Front, Yasin Malik, was among those arrested in Srinagar.
Police have also used tear gas and batons to disperse demonstrators protesting against Mr Malik's arrest.
Elections are to be held in the region in seven phases from mid-November until mid-December.
Thousands of people joined four different protest rallies held on Wednesday evening by various Kashmiri separatist groups calling for the election boycott.
The police have also arrested Ghulam Nabi Sukjhi , who is the acting president of the separatist All Party Hurriyat Party Conference (Geelani group). Another prominent figure, religious party leader Moulvi Showkat, was also taken into custody.
The authorities so far have not commented on the arrests.
But the arrests have triggered sharp criticism from other leaders.
"It clearly indicates the frustration of the government. We are not using any force. We have a democratic right to tell people not to vote," Mirwaiz Umar Farooq, chairman of the All Parties Hurriyat Conference told the BBC.
The state has seen some of its biggest pro-independence demonstrations in the past few months, with hundreds of thousands of people joining marches organised by separatist groups opposed to Indian rule.