Nicaraguan anti-canal activist says held without charge

Medardo Mairena on a video posted on social media that he came home to Nicaragua from Costa Rica, where he visited his son in hospital, and was arrested "without any warrant out for my arrest, and without having committed any crime."

He was released Sunday. Authorities offered no immediate explanation.

The Nicaraguan Human Rights Center said in a statement that Mairena's arrest was a repressive move meant to intimidate "everyone who defends their land from the threat posed by the planned canal."

Nicaragua has authorized Chinese firm HKND to build and operate the canal.

Activists estimate that between 30,000 and 120,000 people could be displaced from their land by the development.

They have challenged the $50 billion project at the Inter-American Court of Human Rights.