Prime Minister Malcolm Turnbull and leaders from the 10 Association of Southeast Asian Nations discussed the issue "at length" on Sunday as they wrapped up a special three-day summit in Sydney.

Myanmar's de facto leader Aung San Suu Kyi has faced international condemnation over her muted response to violence against Rohingya in the troubled Rakhine state, which the United Nations dubbed a "textbook case of ethnic cleansing".

More than 700,000 people have escape to refugee camps across the border following a military crackdown in August.

The leaders put the issue in the too hard basket and did not specifically refer to it in the official communique.

Singapore Prime Minister Lee Hsien Loong described the crisis as a complex situation dating back centuries.

Myanmar is a majority Buddhist country and Rohingya Muslims face discrimination and are denied citizenship.

"Intense public attention sometimes makes it too difficult to solve," Mr Lee told reporters.

"It is of concern to all ASEAN countries and yet ASEAN is not able to intervene and force an outcome."

Instead the countries were focused on providing humanitarian assistance.

Mr Turnbull is due to hold bilateral talks with Ms Suu Kyi in Canberra on Monday.

"Everyone seeks to end the suffering," Mr Turnbull told reporters.

"Our goal is to support a peaceful and speedy resolution of the humanitarian disaster that has resulted from the conflict."

The calls for help from Myanmar come after Malaysia's Prime Minister Najib Razak warned that thousands of desperate Rohingya people could easily be potential recruits for Islamic State.

Mr Lee said while he didn't have specific intelligence supporting Mr Najib's fears, "these are possibilities which you cannot rule out".

Meanwhile, Mr Turnbull characterised Australia as an "all weather friend" to ASEAN and talked up the prospects for greater economic ties.

Now that the Trans-Pacific Partnership free trade pact is signed, the focus has shifted to a swift conclusion to negotiations for a Regional Comprehensive Economic Partnership deal which includes the full ASEAN bloc as well as China and India.

"If we secure a good agreement... this would be an antithesis to protectionism," Mr Turnbull said.

"It would ensure, on the back of the TPP 11, that the Indo-Pacific continues to be the fulcrum of open and free trade."

The leaders walked a cautious line on the tensions in the South China Sea, where Beijing has been building artificial islands to use as defence bases.

Vietnam, Malaysia, Philippines and Brunei claim disputed maritime territory along with China.

The official declaration emphasised the importance of non-militarisation and the exercise of self-restraint.

Mr Turnbull said leaders looked forward to an early conclusion to negotiations between ASEAN and China on a binding code of conduct that would enable freedom of navigation and overflight.

Mr Lee said talks would start this year.

"This is an issue that can not be solved in a short period of time, we have to accept that and work together in good faith," Mr Lee said.

The leaders' had tougher talk on North Korea's nuclear weapon testing program and expressed "grave concerns about the escalation of tensions" on the Korean Peninsula.

The leaders also signed a counter-terrorism agreement on Saturday to boost co-operation amid the threat posed by foreign fighters returning to the region from the Middle East and a Islamic State insugency flare up in the southern Philippines.

The package includes sharing information, removing barriers to police cooperation across borders, ensuring counter-terrorism laws are best practice, as well as tackling terror financing and radicalisation.

Australian Associated Press