George Clooney, his father and several US Democratic congressmen were earlier arrested outside the Sudanese embassy in Washington.
The Hollywood actor, who is president of United to End Genocide, was handcuffed and taken away in a police van for civil disobedience.
The campaigners were demonstrating about the humanitarian crisis in the area between Sudan and South Sudan - which gained independence in 2005 - that is reportedly threatening the lives of over 500,000 people.
Moments before Clooney's arrest, the actor delivered a speech on the steps of the embassy where he called for aid to be sent to Sudan "immediately".
The protesters were demanding that Sudan's President Omar al Bashir ends the blockade that they say is preventing food from reaching people in the Blue Nile regions and Nuba Mountains.
The actor, who was later released, said to ITV News "it was worth a criminal record" to highlight the plight of the people in Sudan.
The 18 arrested today included:
- George Clooney - Actor
- Nick Clooney - Father of George
- Tom Andrews - President of United to End Genocide and former congressman
- Martin Luther King III
- John Prendergast - Enough Project Co-Founder
- Ben Jealous - National Association for the Advancement of Colored People President
- Congressmen Jim McGovern, Al Green, Jim Moran, John Oliver (all Democrats)
- Other Human rights and faith leaders