Overlapping claims by several Asian nations to parts of the resource-rich sea have led to high tensions, especially with China, which claims almost the entire territory.

Indonesia's exclusive economic zone overlaps with China's claim.

And while Indonesia does not claim any of the islands in the disputed Spratley or Paracel chains, it does claim the Natuna islands, which China recently claimed as its own. Vietnam also claims part of the sea.

Vietnamese prime minister Nguyen Tan Dung, on his first state visit to Jakarta since his reelection in July, said his country and Indonesia needed to better patrol their border.

"We agreed to task our foreign ministries with negotiating and signing an agreement to establish joint patrols in the sea area and lines of communication between our two navies," Dung said.

Vietnamese poachers are often found in Indonesians waters, where authorities have seized hundreds of trespassing vessels in recent years.

"We agreed effective cooperation in the field of maritime affairs and fisheries is needed to bring benefits to both countries, including the prevention of illegal fishing," Indonesian President Susilo Bambang Yudhoyono said.

Indonesia loses around 30 trillion rupiah ($3.5 billion) each year because of illegal fishing in its waters, according to ministry figures, prompting the passage of a law in 2009 that allowed marines to shoot and sink poaching vessels.

The neighbouring nations also agreed to increase trade, from $3.3 billion in 2010 to $5 billion by 2015, and sign a rice cooperation framework to ensure food security for all 10 Southeast Asian nations in the Asean bloc.

By Bay Ismoyo - Agence France Presse - September 15, 2011