Media playback is unsupported on your device Media caption George Clooney: 'We were all in a cell together. It was nice"

George Clooney has been arrested for civil disobedience during a demonstration outside Sudan's embassy in Washington DC on Friday.

The actor was taking part in a protest to warn of a humanitarian crisis in the volatile border area between Sudan and South Sudan.

He was detained alongside his father, Nick, but both have now been released after paying bail of $100 (£63).

George Clooney is a keen Sudan activist and has visited the area several times.

South Sudan celebrated its independence from Sudan in 2011, but relations between the two neighbours have worsened since then.

The country is one of the world's poorest regions and has hardly any roads, railways, schools or clinics as a result of two decades of conflict leading up to independence from Sudan in July 2011.

Bitter disagreements remain over oil resources and borders, with conflict raging in the border region - the focus for Clooney's concern.

'We hope it helps'

Speaking to reporters following his release, Clooney said his key concern was the fate of those in the region.

"Best estimate is tens of thousands of people are going to die from starvation... this isn't a famine, this is a man-made tragedy by the government of Khartoum to get these people to leave."

"You never know if you are accomplishing anything... We hope it helps," Clooney said.

Media playback is unsupported on your device Media caption George Clooney gives evidence to US Senate Foreign Relations Committee

The actor said the arrest was his first, but added: "Let's hope it's my last."

The Hollywood star, his father and fellow activists had been led away in handcuffs after reportedly ignoring repeated police warnings to leave the embassy grounds.

He was released three hours later after paying the bail fee.

Secret Service spokesman George Oglivie told the BBC how the arrest unfolded: "George Clooney was arrested for crossing a police line at the Sudan embassy and he'll be transported to the Metropolitan police department second district."

Also arrested, said Mr Oglivie, were Martin Luther King III, son of the civil rights leader; Massachusetts Democratic Congressman Jim McGovern; Virginia Democratic Congressman Jim Moran; and National Association for the Advancement of Colored People President Ben Jealous.

George Clooney's arrest comes a day after he met President Barack Obama at the White House to discuss the Sudan situation.

Ahead of the rally, he said he thought the president was "very engaged" on the issue of Sudan.

Clooney also called on the Sudanese government to allow humanitarian aid in to the area immediately and to "stop randomly killing its own innocent men, women and children".

The actor recently secretly travelled across the border to the Nuba Mountains in Sudan, where his group apparently witnessed a rocket attack. A YouTube video of the visit was uploaded on Thursday.

He told the US Senate Foreign Relations Committee this week that what was happening in the region was "ominously similar" to the violence in Darfur.

The UN estimates that nearly 300,000 people have died and 2.7 million been displaced since the Darfur conflict broke out in 2003.