Whistling is one of the strategies activists use to protest safely, according to one protest organizer, who says that there isn't any way to protest the government or president "without being beaten or fired on by the police."
The 15-day state of emergency will allow authorities to increase security, impose a curfew, and restrict the movement of goods and people, according to an announcement on state television.
Former Chadian dictator Hissene Habre had to be carried into court and restrained by masked security guards at the re-start of his trial for crimes against humanity.
There were claims last week that Islamic State-affiliated militant group Boko Haram had a new leader, fuelling claims that Abubakar Shekau had died. He's now reportedly released a new audio message.
The president claimed that Boko Haram has a new leader, and said the fight against the Nigerian militant group would be over "before the end of the year."
The short-lived rule of rebel leader-turned-president Michel Djotodia.