MUNICH, Germany (Reuters) - South Sudan has deported three U.S. citizens, two of whom served in the military and a third who deserted, U.S. and South Sudanese officials said on Wednesday, another chapter in an unusual tale of unofficial foreign interventions in the country.

Social media accounts and a magazine interview in the names of two of the men suggested they had recently been fighting pro-Russian forces in Ukraine.

Craig Austin Lang, William Wright-Martinovich and Alex Zwiefelhofer were detained on June 21 trying to cross to South Sudan from Kenya, said Lieutenant Colonel Joe Buccino from America’s 82nd Airborne Unit.

They were deported to Kenya, he added.

Private First Class Zwiefelhofer was absent from the 82nd without leave, he said.

“We are working with U.S. authorities in the area to return Private First Class Alex Zwiefelhofer to U.S. military control. They are in Kenya,” he said in an email.

It was not clear when the three were transferred to Kenyan custody. Kenyan authorities did not return calls seeking comment.

South Sudanese foreign affairs ministry spokesman Mawien Makol said the three had been deported because they did not have visas but said they may have claimed to be journalists.

“I heard about three American journalists who were detained on the border between Kenya and South Sudan because these journalists had not received visas,” he told Reuters.

South Sudan’s four-year-old civil war has displaced more than three million people and briefly sparked a famine earlier this year.

A Facebook page and Instagram account in Zwiefelhofer’s name show him in military uniform and photographs of flags, weapons and buildings that appear to have been taken in Ukraine, where foreign volunteers are helping to fight pro-Russian separatists.

Foreign citizens have showed up in South Sudan’s conflicts before, when it was fighting neighboring Sudan before independence in 2011.

The life of former drug addict turned pastor Sam Childers featured in the 2011 movie “Machine Gun Preacher”, although officials later cast doubt on some of his story.

In 1991, British aid worker Emma McCune married rebel fighter Riek Machar, who is leading the rebellion in the current civil war. She died in a car accident in 1993.