"The cruelty and brutality against the rhino, as symbol of our ecology and rich heritage, has gone too far," she said in a statement.
"Recent incidents dictate for extraordinary measures to protect our tourism and biodiversity."
Modise was reacting to the poaching of seven rhinos at the Klipkopspruit Farm, near Rustenburg, on Friday.
The Hawks confirmed on Monday that another rhino was poached at the weekend, but could not immediately provide details.
Modise said there was also a need to clamp down on illegally issued hunting permits.
Communities in the proximity of gameparks and farms also need to be educated and actively involved in nature conservation, tourism and anti-poaching strategies.
The International Fund for Animal Welfare (IFAW) said this weekend's killings showed the "relentless and bloody onslaught" against African wildlife for profit.
Of the eight rhino killed, seven were adults and one a calf.
"Shockingly, the animals were also mutilated for their eyes and ears, while one female had her genitalia cut off," IFAW said in a statement.
The latest killings bring the total number of rhinos killed in South Africa this year to 558, up from 448 in 2011 and 333 in 2010, it said.
"The killing of rhinos for their horns does not exist in a vacuum, but is a complex problem where values of tradition and culture have been corrupted in the name of commercial exploitation," said IFAW director Jason Bell.
"Be it elephants and ivory, tigers and tiger parts, rhinos and rhino horn, the endpoint is the same – profit. And that profit is being chased down in the most brutal fashion by organised crime syndicates who are fearless in their pursuit of the prize."
Bell said the last 24 months had been the most "deadly ever" for elephants and rhino.
The biggest market for rhino horn is China, where it is used mostly in the manufacture of traditional medicine. – Sapa