JUBA, South Sudan (AP) — South Sudan's vice president is urging regional mediators to intervene to protect the country's fragile peace deal, warning of a return to war amid alleged attacks by government troops on his forces.

Riek Machar accused President Salva Kiir of violating a 2018 truce in a letter to the regional mediator, the 8-nation Intergovernmental Authority on Development, or IGAD.

“The security situation in South Sudan has been deteriorating for the last few months,” Machar said in the letter. “Therefore, we request, as a matter of urgency, the intervention of IGAD and other international partners to prevail on President Salva Kiir not to take this country back to war.”

There was heavy military deployment in the capital, Juba, Monday near the international airport and the presidential palace, highlighting growing tensions.

Puok Both, a spokesman for Machar, confirmed the deployment of government troops in parts of Juba, saying “we don’t know their intentions.”

It was not immediately possible to get a comment from the presidential spokesman.

South Sudanese government troops and forces loyal to Machar have recently clashed in Upper Nile and Unity states, which are seen as Machar’s strongholds.

There were high hopes for peace and stability when oil-rich South Sudan gained its long-fought independence from Sudan in 2011. But the country slid into civil war in December 2013 largely based on ethnic divisions when forces loyal to Kiir battled those loyal to Machar.

Tens of thousands of people were killed in the civil war which ended with a 2018 peace agreement that brought Kiir and Machar together in a government of national unity.

But challenges remain, including the government’s failure to implement promised reforms including completing the unification of the army command.

Kiir on Friday issued a decree in which he offered five command positions in the army and the police to his rivals, a unilateral decision opposed by Machar.

The U.S., the U.K. and Norway — the troika supporting South Sudan’s peace deal — said last week they were concerned that the new outbreak of fighting threatens to undermine the government’s unity.

A group of United Nations experts warned in a report last year that “the stability of South Sudan has remained at risk” as a result of missed deadlines and political gridlock on key issues in the unity government’s agreement.