Lalmalsawma told PTI that the national flags would be flown at half mast and no official entertainment would be organised during the three-day mourning period.
Official obituaries would also be issued on the deaths of the two leaders, he said.
When asked whether Sailo would be accorded a state funeral with full honours, the chief secretary said that no such proposals have been received so far.
Sailo died of heart failure at the New Life Hospital in Aizawl this morning while Kyndiahdied at the Bethany Hospital in Shillong last night.