Italian energy giant Eni announced the discovery of the "largest ever" offshore natural gas field in the Mediterranean, in Egypt's territorial waters.
The discovery, confirmed by Egypt's oil ministry, could hold a potential 30 trillion cubic feet (850 billion cubic meters) of gas in an area of about 100 square kilometers (40 square miles), Eni said in a statement.
"It's the largest gas discovery ever made in Egypt and in the Mediterranean Sea and could become one of the world’s largest natural-gas finds," the firm said.
The so-called Zohr project discovery is expected to meet Egypt's own natural gas demands for decades.
The "supergiant" field is located at a depth of 4,757 feet (1,450 meters) in the Shorouk Block, Eni said.
The firm said it would "immediately appraise the field with the aim of accelerating a fast track development of the discovery", giving a timeframe of four years.
It added that Eni's CEO, Claudio Descalzi, has visited Cairo and discussed the discovery with Egyptian President Abdel Fattah al-Sisi and Prime Minister Ibrahim Mahlab.
"This historic discovery will be able to transform the energy scenario of Egypt," Descalzi said in the statement.
Italian Prime Minister Matteo Renzi, in a message to Descalzi, congratulated the oil company on the "extraordinary" discovery.
"A find of this size should be enough to cover a lot of Egypt's energy gap," Robin Mills, a Dubai-based analyst at Manaar Energy Consulting, told Bloomberg News.
"They'll likely have to meet domestic needs first, before any export plans are discussed. This will also put a damper on Israeli plans to export gas to Egypt," he added.
Egypt, the largest country of the Arab world, is of strategic and economic interest to Italy. It the first country Eni expanded to some 60 years ago from its base in Italy.
Previously Italy invested heavily in neighboring Libya, but for the past four years Libya has been mired in chaos and violence.
In recent years the western Mediterranean has seen a jump in gas exploration. In 2010, major natural gas fields found off Israel.
In March, British energy giant BP unveiled plans to invest $12 billion (10.7 billion euros) in Egyptian offshore gas fields with Russian partner DEA, despite the slump in world oil prices.
It said the investment in the West Nile Delta fields aims to develop five trillion cubic feet of gas resources and 55 million barrels of condensates, with output expected to begin in 2017.