"Ondala was punched several times in an attack by disgruntled players at a Heritage Tournament in Tsholomnqa and required hospital treatment," SARU said in a statement on Friday.
The assault was alleged to have related to unhappiness surrounding an eligibility ruling by the BRU against the players' club.
"An assault is unacceptable in any circumstances, but for players to take out their unhappiness about an off-field administrative decision in this fashion is outrageous," said SARU president Hoskins.
"The matter is now in the hands of the police, as it properly should be, and I hope that this matter will be pursued to the full extent of the law.
"This is a very sad occurrence and has no place in rugby."
Hoskins said he expected a report from the BRU executive on its plans for disciplinary action against any club members who were involved.