Nasa leader Raila Odinga said Sunday he would announce his strategy on Tuesday after an election he claims was stolen from him, and told his supporters to stay away from work.
"We had predicted they will steal the election and that's what happened. We are not done yet. We will not give up.
"Wait for the next course of action, which I will announce the day after tomorrow," he told a heaving crowd of supporters in Nairobi's largest slum, Kibera.
"But for now I want to tell you not to go to work tomorrow (Monday)."
Residents of Kibera climbed on roof tops and hung off trees to catch sight of Mr Odinga, who was speaking for the first time since his rival President Uhuru Kenyatta of Jubilee Party was declared the victor Friday in a poll he claims was massively rigged.
The decision sparked immediate protests in Mr Odinga's strongholds in western Kenya and Nairobi slums including Kibera and Mathare, which have left at least 16 people dead.
"This is a failed regime that is resorting to killing people instead of addressing the real issue. The vote was stolen. There's no secret about that," Mr Odinga said.
READ: Gunshots, protests in Nasa strongholds - VIDEO
His comments come after a chorus of calls from the international community for him to calm his supporters.