I skip the already mentioned bands, as it seems, that a lot of old demos are currently re-released on CD, so easy to check out.
Anal Vomit - the Sarcofago of Peru. Incredible brutal stuff. Their latest release is availabe as LP on From Beyond Prod.
Disinter - one of the 500 exisiting bands with this bandname. Old-school Death Metal, but average production. Their latest CD "Hell's Gate" sounds quiet cool though. Typical South American Death Metal.
Epilepsia - great Thrash. Thrash Thrash Thrash. Not the Witchtrap way, which means too much 80es rip-off, but still a lot of 80es/early 90es influences.
Estigma - The Bloodstained God CD, great Thrash. Very old band, and completly ancient Thrash mixed with some folky South American parts.
Goatsemen - wow, there part on the Split CD with Anal Vomit rules. Dark Death Metal, with hints of Black and completly old-school.
Hadez - their Aquarelle CD on Brutal Records was most probably the first extreme Metal CD from this counrtry. Horrible booklet layout which doesn't fit at all in the jewel case. I wonder if this is only in my CD ? Also similar to Sarcofago. If you like INRI, you like this Hadez release.
Kranium - folky Death Metal. Very nice to listen to.
Pagapu / Sarcoma Split CD. Also very folky Death Metal meets old South American Death Metal. Great old bands from Peru
I hope that helped. Still, Mortem is my absolute favourite out of this country.