Sierra Leoneans have been rallying against the high cost of living, corruption and police brutality. There are also calls for President Julius Maada Bio to step down.
Some protesters and policemen were killed on the third day of violent protests that have taken place in the capital, Freetown, as well as several other towns.
The government on Wednesday imposed a nationwide curfew in response.
In a statement in Abuja, Ecowas called on all to obey law and order and for the perpetrators of the violence to be identified and brought to justice.
Protesters on Wednesday blocked off the main entrance into the country’s Lungi airport and clashed with security agencies.
President Bio is currently out of the country with his family and has left Vice-President Mohamed Juldeh Jalloh in charge.
The vice-president announced the curfew on Wednesday in a short state broadcast.
He said security forces had been authorised to deal with lawbreakers, accusing the protesters of destroying and burning down public facilities.
Sierra Leone is due to go to the polls next year to elect a new president. The protesters say that President Bio should not seek re-election.