South Sudan's government has denied earlier reports that Uganda had deployed special forces to its capital, Juba.

Uganda's military chief Gen Muhoozi Kainerugaba said the soldiers had gone to the neighbouring country to help South Sudanese President Salva Kiir "secure" the city.

The statement came amid escalating tensions between Kiir and his deputy Riek Machar, raising fears that their fragile peace deal could collapse and a conflict could resume.

"We shall protect the entire territory of South Sudan like it was our own," Gen Kainerugaba had written on the social media platform X.

Uganda's army spokesperson Felix Felix Kulayigye also confirmed the deployment to the BBC but declined to reveal details.

South Sudan's government did not immediately respond to the reports on Tuesday morning, but speaking to local media later Information Minister Michael Makuei said Ugandan troops were not in Juba.

Concern about the security situation in South Sudan has been mounting, with the US on Saturday ordering the evacuation of all its non-emergency staff from the country.

Last week, the deputy chief of the army and two ministers - all allies of Machar - were arrested by the security forces, which an opposition spokesman called a "grave violation" of the peace deal.

One of the ministers has since been released.

The arrests followed clashes in the Upper Nile state between government forces and a militia known as the White Army.

It had fought alongside Machar during the civil war that broke out in 2013 following a power struggle between him and Kiir.

It led to heavy fighting in Juba, with Kiir accusing Machar of plotting a coup.

Machar denied the allegation, but South Sudan then plunged into a civil war that killed more than 400,000 people.

A 2018 power-sharing agreement between the two stopped the fighting, but key elements of the deal have not been implemented - including a new constitution, an election and the reunification of armed groups into a single army.