Witnesses speak about Charl Kinnear killing
A further four people - three women and one man - were injured during the incident. They were rushed to Grey hospital to receive treatment.
Firefighters managed to get the fire under control and saved a "few" people who were still alive and trapped inside.
"All the victims' ages cannot be confirmed."
Six charges of murder and arson have been opened.
"The cause of the bombing is unknown at the moment and it forms part of the investigation. A 72-hour activation plan has been initiated, while the case has been handed over to the DPCI [Hawks] for further investigation and handling," said Soci.
Eastern Cape police commissioner Lieutenant-General Liziwe Ntshinga expressed her shock at the incident.
"No words are enough or appropriate to express our shock at the inhumane and brutal way the victims suffered at the mercy of the perpetrators," Ntshinga said.
"Our detectives must leave no nook and cranny uncombed in search of the perpetrators behind this cruel act.
"We have initiated a 72-hour activation, and in the same breath send our sincere condolences to the victims, their families and close relatives."