JUBA (AFP) - South Sudan rebels loyal to fugitive former vice president Riek Machar have seized the key town of Bor, the army said on Thursday, as fighting continued following an alleged failed coup bid.

"Our soldiers have lost control of Bor to the force of Riek Machar late on Wednesday," said army spokesman Philip Aguer. "There was shooting last night... we don't have information on casualties or the displaced in the town, as operations are ongoing."