Britain's BG Group and Australia's Woodside Petroleum Ltd will invest up to $1.08 billion (0.72 billion pounds) to explore for oil and gas in four blocks off the coast of Myanmar's western Rakhine state, a senior Energy Ministry official said.

The two firms were the winners of two shallow water blocks and two deepwater blocks in the country's auction last year.

"Operations at the shallow blocks will take $545.5 million at the minimum, while that at deep-sea blocks will cost $535.1 million at the minimum," said the official, who declined to be identified, as he is not an authorised spokesman.

The two companies signed production-sharing contracts with the energy ministry in Myanmar's capital of Naypyitaw, he said, adding that observation and exploration work at the blocks will take another seven or eight years.

Myanmar's oil and gas sector attracted $2.6 billion, or about 40 percent of foreign investment of $6.6 billion during the nine months to December, the website of the country's Central Statistical Organisation (CSO) shows.

Myanmar's proven natural gas reserves totalled 10 trillion cubic feet (tcf) at the end of 2013, according to BP's Statistical Review of World Energy. Neighbouring Thailand imports about a fifth of its natural gas supplies from Myanmar.