The US military has used a secret technology to spy on North and South Sudan, but the United Nations is calling for the United States to reveal its role.US Secretary of State John Kerry said on Tuesday that the Pentagon had deployed a “black box” to spy satellites.

He said the technology was used to track the location of satellites, including the one he described as a secret spy satellite.

Mr Kerry told reporters in New York that the equipment, which the Pentagon calls the DRC Black Box, was used “to monitor the movements of the satellites that were in orbit over the African continent, which is the same way we monitor satellites around the world”.US Defence Secretary Chuck Hagel, in a news conference on Tuesday, said the spy satellite had been deployed to track South Sudan’s satellite, the Joint Global Positioning System, and the military had been able to pinpoint the position of its satellite to about 3,500km away.

The Pentagon said it had been “blindsided” by the satellite’s presence.

Mr Hagel said the military was using the technology to “detect and track the movements and activities of the Sudanese military”.

“It is not possible to know for sure what we’ve got because the Sudan is not allowed to say, but I would venture to say that this is a very, very sophisticated, very accurate piece of technology,” he said.

The Sudanese army has been accused of violating the 1994 Armistice Agreement by attacking South Sudan in the south and north.

South Sudan’s military said the satellite, which had been on a “very short” flight from Washington to DRC, was “unrelated” to the attacks and said the equipment had not been used in any previous incidents.

It is also not clear why the DSCS satellite had come to the region, which borders Sudan and the Democratic Republic of the Congo, a country which has fought a civil war for decades.

The US-backed government says it has launched a military offensive against South Sudan to dislodge the secessionist government.

Sudanese troops are also fighting rebel groups in neighbouring Congo, and in August, the US military said it was using drones and satellites to track Sudanese rebel fighters in the region.

The White House said on Monday that the military would not target South Sudan without UN approval.US Senator Joe Manchin, a Democrat from West Virginia, told reporters at a briefing in Washington that the US was concerned about “a potential future escalation of conflict” and that the war in South Sudan had to stop.

He called on the UN to “prohibit the use of weapons that are indiscriminately killing civilians”.

“This is a military conflict, and if the UN does not act, the situation in South Africa, which will be the target of this action, is going to get much worse,” he added.US Vice President Joe Biden is due to meet with South Sudanese President Salva Kiir in Washington on Thursday.

Mr Biden said in a statement that the two leaders “share a deep appreciation for the dignity and resilience of the people of South Sudan and that their efforts to reunify the country are consistent with the United Nation’s values”.

“We are committed to holding the Government of South Africa accountable for the abuses it has committed in South, and will continue to work to bring the perpetrators to justice,” he wrote.

Srebrenica genocideA genocide by the Bosnian Serbs of Bosnia against Bosnian Muslims in the 1990s, the largest genocide in modern history, has triggered a global outcry and the United Kingdom has vowed to extradite the killers to the US to face trial.

The UN has called for the Bosniak authorities to be prosecuted and for a peace deal with the Muslim-majority country to be signed.

Sri Lanka’s Prime Minister Sivanara Theraweera, a close ally of Mr Kerry, also called on Mr Kerry to take action, saying that he should not be silent in the face of atrocities.

“If he does not make it clear that the United State is responsible for the atrocities that are being committed by the government of the Republic of Sri Lanka, then he will be complicit in the perpetuation of such atrocities,” she told reporters.

“We have to stop the genocide of our people and stop the impunity of the leaders of the regime,” Ms Theraweyera said.

In April, the UN General Assembly voted to impose sanctions on Sri Lanka for its role in the genocide, calling for an investigation into the massacre.

“The genocide is a crime and an atrocity,” said UN Secretary-General Antonio Guterres.