Soldiers had invaded the Lekki toll gate area of Lagos earlier on Tuesday, shooting at unarmed protesters.
The incident had generated an uproar, within and outside the country.
In a tweet on Tuesday night, Clinton lent her voice in support of those who had condemned the action of the soldiers.
“I’m calling on @mbuhari and the @hqnigerianarmy to stop killing young #EndSARS protesters,” she tweeted.
— Hillary Clinton (@HillaryClinton) October 20, 2020