A gun amnesty in South Australia has been extended until the end of the year, with more than 2,600 unregistered, illegal or unwanted firearms already handed in since it began.

The amnesty started on December 1, 2015 and will finish on December 31, 2016.

Superintendent Kym Hand said the extension would give owners more time to hand in their firearms and make the community safer.

"The surrender of 2,635 firearms in just six months is a significant response," Superintendent Hand said.

"That response indicates extra time will give more owners the opportunity to clear out firearms, accessories and ammunition, without fear of prosecution for having unregistered or unlicensed firearms and assist to keep them out of the hands of criminals."

Superintendent Hand said from July 2013 to January 2016, a total of 670 firearms were reported stolen in South Australia.

Just over half of those were stolen from owners living in rural areas.

"Police reinforce the message to rural owners that now is time to hand in firearms they no longer need or those that aren't [or never have been] registered," Superintendent Hand said.

"Don't get left with illegal or unregistered firearms and face tough penalties of up to $50,000 or imprisonment for up to 10 years."

Those wanting to hand in guns can find participating dealers on the SA police website.