The border guards were killed after clashes erupted near the town of Mirjaveh in the Iranian province of Sistan- Balochistan which has a border crossing with Balochistan.
Four other border guards were also injured in the clashes, the news agency reported.
The Sistan-Balochistan province is the largest Iranian province in the southeast of Iran and has its borders with Pakistan's restive Balochistan province.
Security forces are often attacked by armed bandits, drug dealers, and outlaws in the area.
In July last year, four Iranian guards were killed in the border region with Pakistan.
The Iranian media has claimed that the Jaish al-Adl militant group - accused by Tehran of links to al Qaeda - carries out regular attacks in Sistan and Balochistan.