International experts have disputed the government's accounts of what happened and have said its investigation was deeply flawed.

In northern Nigeria alone, nearly 1.2 million children – over half of them under 5 years old – have been forced to flee their homes.

The IAEA has said it has a legal obligation to keep details of the arrangement confidential, but insists it is technically sound.

The recent Islamist offensive has highlighted the group's ability to keep up the pressure on the Western-backed government it wants to topple.

Ponta faces charges of fraud, tax evasion and money laundering dating back to his days as a lawyer before he was elected PM in 2012.

That follows a massacre at a military-run school last December that killed around 150 people, almost all of them children.

Jose Cabanas is a veteran diplomat who has run Cuba's "interests section" in Washington since 2012.

Only the main Bajakovo crossing, on the highway between Belgrade and Zagreb, appeared to be open to traffic.