NAIROBI, Kenya -- In a move that’s likely to shake the foundations of the world’s youngest nation, the eldest son of South Sudan’s founding hero has broken his family’s political silence and declared his opposition to the country’s leadership.

It’s another indication of the depth of concern over the direction of a country whose existence in one of the world’s most volatile regions depends on U.S. backing.

Mabior Garang has accused those who took power after the death of his father, guerrilla leader John Garang, in a 2005 helicopter crash of pulling a "posthumous coup," and he urged others to speak out in opposition.

"My father is a fuel by which these people have been running, but they have actually gone against (him). They’ve done the opposite of what he was saying and what he was trying to do," said the younger Garang, whose face is a tauter, youthful version of his late father’s. “I’m opposed to what’s happening. I don’t want to be guilty by association."

In a lengthy interview with McClatchy in the Kenyan capital, Garang said the government had been trying to intimidate him into silence after he posted critical remarks on his Facebook page. He wore a sling on his right arm, the result of a recent assault in Juba, South Sudan, for which he blamed the president’s security service.

"I’m not worried, but I am in danger,” said Garang, who claims that he survived an attempt on his life in 2008. “I’ve already been attacked. My jaw is broken in three different places."

The younger Garang’s decision to take his views public rolls back the curtain on one of the long-standing rifts within South Sudan’s ruling party. After independence, many of those close to John Garang were sidelined as President Salva Kiir shored up his own political base. That fault line remains, especially in the military.

Diplomats knew that South Sudan’s emotional march to independence superficially chalked over the young nation’s deep internal divisions. After independence, that solidarity was expected to splinter: in the best case into a multiparty democracy; in the worst case, civil war.

Nevertheless, the government has promoted the late rebel founder as a near-mythological, heroic figure. Garang founded the Sudan People’s Liberation Movement in 1983 and led it until his death.

South Sudanese officials declared the anniversary of his death a national holiday – Martyr’s Day – and held their independence celebrations last year at the John Garang memorial, where they unveiled a new statue of the U.S.-educated political activist.

The young Garang was openly disdainful of the public displays honoring his father, gestures he views as disingenuous and hypocritical.

"They are fake statues,” he said. “The ones they made at independence were made out of cement, but (made) to look like copper. It was not even cast."

In the interview, Garang offered a long list of grievances against the nation’s leaders, labeling them an authoritarian elite and part of a political culture that’s too comfortable with soliciting violence for power.

His family is especially upset by the public murder of a Kenyan teacher who was employed at the school his family runs. The teacher was killed in May by a member of the president’s personal militia because she didn’t stop driving as the South Sudanese flag was being raised. His family has hired lawyers to prosecute the case.