The kings and emirs of the Arab states met privately for nearly three hours in Riyadh Saturday in what a Gulf Cooperation Council statement described as a "consultative" summit.
Discussions during the one-day gathering tackled developments in Iran, Iraq and combatting terrorism, United Arab Emirates Foreign Minister Sheik Abdullah bin Zayed Al Nahyan told journalists on behalf of the GCC leaders after they finished their talks.
"Iran should be transparent in dealing with the region," regarding its nuclear program, Al Nahyan said.
The Gulf nations will seek guarantees against "environmental hazards " potentially posed by Iranian nuclear reactors, he added.
Members of the GCC, a loose military and political alliance, are increasingly nervous about Iran's disputed nuclear program. Iran is just across the Gulf from council member countries.
Some have voiced concern about the Bushehr reactor, near Iran's coast across the Gulf from Saudi Arabia and some 300 kilometers (186.42 miles) from Kuwait.
"Iran's nuclear dossier is worrying, not only to the region but to the world," Al Nahayan told reporters, urging Iran to cooperate with the International Atomic Energy Agency and the international community to resolve the standoff.
Al Nahyan also alluded to concerns expressed by some Gulf nations, which are predominantly Sunni Muslim, about a Shiite-dominated government in Baghdad closely tied to Shiite Iran.
"If there is Iranian intervention in Iraq, let it be only to bring Iraqi points of view closer together."
Describing terrorism as an "issue that affects the region directly," Al Nahayan said the leaders welcomed Bahrain's efforts to establish an international intelligence-sharing center to combat terrorism.
Ahead of the summit diplomats predicted that the freezing of funding to the Hamas-led Palestinian government would figure in the talks, but Al Nahayan did not mention the issue.
The GCC comprises Bahrain, Saudi Arabia, Kuwait, Oman, Qatar and the UAE.