Senior separatist leaders were placed under house arrest here on Tuesday so that the Republic Day celebrations were not disrupted.Police sources said Syed Ali Geelani, Mirwaiz Umer Farooq, Muhammad Yasin Malik and Shabir Shah were put under house arrest to prevent them from disrupting the official functions.The separatists had asked people to observe January 26 as a "black day" to attract international attention to the Kashmir issue.