Ceasefire monitors have begun work in South Sudan, officials said Monday, amid repeated claims both government and rebels are breaking a deal to stop weeks of bloodshed in which thousands have been killed.

Ceasefire monitors have begun work in South Sudan, officials said Monday, amid repeated claims both government and rebels are breaking a deal to stop weeks of bloodshed in which thousands have been killed.

Clashes continue despite the deal signed last month by government and rebels, brokered by the East African bloc, the Intergovernmental Authority on Development (IGAD).

"Some monitors have come," South Sudanese Vice-President James Wani Igga told reporters on Monday.

Thousands are believed to have been killed in the fighting pitting forces loyal to President Salva Kiir against a loose coalition of army defectors and ethnic militia nominally headed by sacked vice president Riek Machar, a seasoned guerrilla fighter.

The advance 14-person strong IGAD team -- led by an Ethiopian general with a Sudanese deputy -- arrived on Sunday and will report back on February 7 to IGAD special envoys in Ethiopia, when rival forces are due to restart peace talks.

IGAD teams are meant to ensure the warring sides honour their deal, but many fear the unarmed observers will struggle to monitor loose frontlines between multiple forces in a vast country with few roads.

The team will investigate "areas for possible deployment of the monitors", IGAD said in a statement.