Juba (AFP) - South Sudan's president and his estranged deputy ordered a ceasefire on Monday after a new day of heavy fighting in the capital that sent thousands fleeing and threatened a return to civil war.

President Salva Kiir's ceasefire order Monday evening was followed by a similar call from ex-rebel and Vice President Riek Machar, raising hopes of an end to three days of deadly fighting between the army and former rebels in the world's youngest nation.

"The president has reiterated his commitment to the continued implementation of the (peace) agreement in letter and spirit, and thus issues an order of cessation of hostilities with immediate effect," Information Minister Michael Makuei said on state television at 6:00 pm local time (1500 GMT).

Machar, a former rebel, then asked troops loyal to him to stop fighting.