Iranian officials say the Saudi coast guard has fired on two fishing boats in the Persian Gulf, killing one fisherman.
Iran's Interior Ministry said Saudi authorities claimed the boats drifted into Saudi waters when the incident happened late on June 16.
"We are pursuing this matter to determine if the Iranian boats had crossed the Saudi border or not, but the action of the Saudis does not comply with humanitarian and navigational principles," Iran's June 17 statement said.
Saudi Arabia has not commented on the incident.
Iranian state media reported that the incident occurred near an offshore Saudi oil platform.
Relations between the two regional rivals have been tense for some time, and they severed diplomatic ties in 2016.
The two countries often support opposite sides in regional conflicts, including those in Yemen and Syria.