All four allegedly involved with the two Z incidents have been arrested.
Later that evening, three other people entered Flaxmere Fast Foods in the Swansea Rd village, Flaxmere. They were disguised with red bandannas and jumped over the shop's counter before assaulting workers and taking money from the till.
Although one of the offenders was held down by shop workers and customers, they escaped, one leaving a shoe behind.
The victims received minor physical injuries, and were shaken by the incident.
Detective Senior Sergeant Brent Greville, of the CIB Hawke's Bay, said four people had been arrested relating to the Z store robberies and they were still following lines of inquiry into the third incident.
He said there was no link between those three robberies and other recent incidents.
"There's no particular 'season' for committing aggravated robberies - we have simply had a spate of robberies in the last few months.
"It is, however, interesting that the reasons for the robberies may be similar as the offenders in these cases have targeted cash or cigarettes and tobacco," Greville said.
A Z Energy Limited spokeswoman said "when robbers undertake crimes like this they put members of their own community at risk".
She said the staff member involved was physically unharmed but was understandably shaken and had been offered counselling.
"Safety of staff is a priority for Z and the company has safety measures in place to deter robberies and help keep staff safe.
"All Z sites keep only a minimal amount of cash on site for security reasons, so in this case the robber has put his freedom in jeopardy for just a small amount of cash."
The spokeswoman said all Z service stations had high-definition CCTV footage, which in both incidents showed offenders' faces clearly.
