At least 10 others have been injured or seriously injured.
Assistant Commissioner Road Policing Sandra Venables says this weekend's fatalities will have left families devastated up and down the country.
"Every death is reported as a number, but each number has a face, a name and a family. They leave behind loved ones whose lives have been changed forever.
"We cannot continue to tolerate the loss."
She said it was too early to give exact details of the causes of the weekend's crashes but speed, fatigue, losing control and crossing the centre-line were all factors.
"We have another long weekend coming up when traditionally more people will be out on the roads. Everybody needs to focus on getting to their destination and home again safely."