The two men, aged 23 and 25, were arrested in a residence in the capital. Police discovered a small arsenal that included a rifle, one shotgun and a number of pistols, among other weapons.
Police said they discovered evidence of travel abroad "along with credentials in Arabic and an image of the Hezbollah flag."
Police did not specify the nature of the travel or credentials, and did not say whether the men had intention of attacking the G20 event.
Security Minister Patricia Bullrich said on Nov. 15 security forces were on the lookout for any suspicious activity ahead of the conference.