DHAKA (Reuters) - A U.N. tribunal has awarded Bangladesh nearly four-fifths of an area sprawling over 25,000 sq km (9,700 sq miles) in the Bay of Bengal, ending a dispute over a sea border with India that has ruffled ties between the neighbours for more than three decades.

The verdict, binding on both countries, opens the way for Bangladesh to explore for oil and gas in the Bay of Bengal, the site of important energy reserves.

“It is the victory of friendship and a win-win situation for the peoples of Bangladesh and India,” Foreign Minister Abul Hassan Mahmood Ali told a news conference on Tuesday to announce the ruling of the Hague-based Permanent Court of Arbitration (PCA) on the sea boundary.

The dispute had hampered the economic development of both countries for more than 30 years, he added.

“We commend India for its willingness to resolve this matter peacefully by legal means and for its acceptance of the tribunal’s judgment,” Ali added.

India also welcomed the judgment, reflecting new Prime Minister Narendra Modi’s focus on building closer regional ties. In a rare gesture, Modi invited South Asian leaders to his inauguration in May.

“The settlement of the maritime boundary will further enhance mutual understanding and goodwill between India and Bangladesh by bringing to closure a long-pending issue,” the Ministry of External Affairs said in a statement.

“This paves the way for the economic development of this part of the Bay of Bengal, which will be beneficial to both countries.”

Bangladesh, with a population of 160 million and strong economic growth, has battled supply shortages to keep its gas-fired power plants and industries running.

The award brings to an end an arbitration process Bangladesh kicked off in 2009 under the U.N. Convention on the Law of the Sea, over disputes with Myanmar and India.

The Myanmar dispute was settled in 2012 after arbitration at the International Tribunal on the Law of the Sea in Hamburg.

Bangladesh finally won more than 118,813 square km of waters comprising territorial sea and an exclusive economic zone extending out to 200 nautical miles, the minister said.