Senior separatist leaders were placed under house arrest here on Thursday ahead of a protest action called by them in north Kashmir's Sopore town on Friday.Restrictions have been imposed on the movement of senior separatist leaders Syed Ali Geelani, Mirwaiz Umar Farooq and Muhammad Yasin Malik in order to maintain law and order, police said.Shahid-ul-Islam, secretary to Mirwaiz Umar Farooq, told IANS here: "At 1 p.m. today (Thursday), police informed Mirwaiz Umar Farooq that he would not be allowed to move out of his Nigeen residence till further orders."While Geelani has been placed under house arrest in his uptown Hyderpora residence in the city, Muhammad Yasin Malik has been taken into preventive custody and lodged at Kothibagh police station here, police said.Separatists have jointly called a protest march to Sopore town on Friday against target killings of former militants in the town.The state government has already announced a reward of Rs.10 lakh each on two militants who, police say, had broken away from pro-Pakistan Hizbul Mujahideen guerrilla group and were responsible for the mysterious killings of four former militants in Sopore town.