At least five South Sudanese workers were killed after attackers stormed their compound in the key Unity oil field, an official in the Chinese-owned company said Thursday, amid wider violence wracking the young nation.

"A group of armed men came to the compound and killed staff" late on Wednesday, a senior official of the Greater Nile Petroleum Operating Company (GNPOC) said, not wanting to give his name as he was not authorised to speak to the media.

It was not clear if the attack was linked to rebel battles with government troops following an alleged failed coup attempt against South Sudan President Salva Kiir.