"Our ties must not be hampered by deeply shortsighted miscalculations, including highway robbery on the command of a 3rd party," Saeed Khatibzadeh wrote in a tweet on Saturday, referring to the US.
He added that Iran's ancient ties with Greece and its great people have always been based on mutual respect.
The Iranian spokesperson also confirmed the crew members of the two seized Greek tankers "are safe and in good health."
Iran's Ports and Maritime Organization (PMO) said on Saturday that the crews of two Greek oil tankers seized by the Islamic Revolution Guards Corps (IRGC) in the Persian Gulf are not detained but are aboard the vessels and in good health.
"All crew members of both Greek ships are in full health and being protected while on board in accordance with international law, and they are provided with necessary services," Iran's maritime body said in a statement on Saturday.
It added that the two Greek tankers were seized due to maritime violations and noted that the issue is under investigation based on evidence and documents.
The necessary legal action will be taken after the completion of the process, the PMO said.
"The Islamic Republic of Iran, as a party to the 2006 Maritime Labor Convention, fulfills its commitments vis-à-vis all seafarers, including the guest seafarers," the statement pointed out.
The IRGC announced in a statement on Friday that it had seized two Greek oil tankers in the Persian Gulf over violations, days after an Iranian oil tanker was captured by Greece in its territorial waters and its oil cargo was transferred to the US.
The Greek Foreign Ministry said later on Friday that Iranian navy helicopters had landed gunmen on the two tankers earlier in the day.
One of them, the Delta Poseidon, was sailing in international waters at the time, the ministry said, adding that the second tanker was near the Iranian coast when seized.
The ministry also said nine Greeks were among the crews of both vessels, but did not give a number of other sailors on board.
MNA/PressTV