New Delhi, Oct 1 : The overseas investment arm of state-run Oil and Natural Gas Corp (ONGC) has secured the government's nod for an additional investment of $149.46 million in a gas block in Vietnam, as part of India's quest for energy security.

The permission was given by the Cabinet Committee on Economic Affairs during a meeting here Thursday presided over by Prime Minister Manmohan Singh, officials said.

ONGC Videsh has a 45 percent participating interest in a gas-producing shallow water offshore block under contract with Petro Vietnam, the national oil firm of the Southeast Asian country of Vietnam.

While the Vietnamese company has a 20 percent share, the remaining 35 percent is with British Petroleum. ONGC Videsh had an initial investment commitment of $228 million.

The production from the fields had started in January 2003 after completion of the first phase of the project. The initial production at 0.81 billion units in 2003 has increased to 4.106 billion units.

The 45 percent share of ONGC Videsh last fiscal amounted to 1.848 billion units.

The third phase of the project envisages development of another field, including the drilling of two wells, sub-sea work, and building of a platform for transport of gas through a common pipeline, officials said.

The revised estimated expenditure for the whole project during 1998-2015 is $838 million against the earlier estimates of $228-$377 million. Accordingly, a nod was sought for a further expenditure of $149.46 million, the officials added.