With options for oil and natural gas expanding, Iranian President Hassan Rouhani said a joint nuclear agreement has strengthened the country's independence.

Iran celebrated Monday the 50th anniversary of a national gas company, a milestone that came roughly one year after the country signed a multilateral agreement to curb nuclear research activity in exchange for relief from some international sanctions.

The president said relief from sanctions meant Iran could expand its trade relations for oil and natural gas, curbing domestic restraints in terms of petroleum products like gasoline while offering more outlets for oil.

"A revolutionary country needs to be independent, for a revolution means the country must be independent and free," he was quoted by the Iranian Oil Ministry's news website SHANA as saying. "This is what a revolution is all about."

Sanctions pressures on Iran started easing in January after the United Nations confirmed compliance with a multilateral nuclear agreement brokered last year. Last month, Iranian oil officials said they were drafting a list of international oil and gas companies eligible to play a role in the energy sector.

Austrian energy company OMV was among the first to sign agreements with Iran in a step toward resuming formal operations. Royal Dutch Shell received a shipment of Iranian crude oil last month after it paid off its debt to its Iranian counterparts early this year.

An Iranian port director said the number of foreign oil tankers docked off the nation's southern coast has increased dramatically since compliance with the nuclear agreement was confirmed.

"For the first time since implementation, 240 oil supertankers carrying various countries' flags loaded at Kharg island," General Manager of Bushehr Province Department of Ports and Maritime Organization Mohammad Mehdi Benchari was quoted by Iranian broadcaster Press TV as saying.