DOHA: Key gas exporter Qatar has discovered additional reserves of 2.5 trillion cubic feet (68 billion cubic metres) of natural gas in a northern offshore field, media reported on Monday.

The discovery was made in Block 4 North, in North Field at a water depth of around 70 metres (230 feet), newspapers said.

The gas discovery was "made after four years of intensive exploration activities, including the drilling of two exploration wells," The Peninsula daily quoted Qatar's energy minister, Mohammed al-Sada, as saying.

The field is operated by Qatar Petroleum and its German partner Wintershall, as well as Japan's Mitsui Gas Development Qatar.

North Field was discovered in 1971 and contains 900 trillion cubic feet of recoverable gas.

Local daily Gulf Times quoted Sada as describing it as "an important gas discovery for Qatar" -- the world's fourth biggest natural gas exporter.

The tiny Gulf peninsula holds the world's third-largest gas reserves and produces roughly 77 million tonnes of liquefied natural gas per year, making it the world's largest supplier.