PHNOM PENH  - Asian leaders Tuesday called for Western sanctions against Myanmar to be lifted after its historic polls, as they held summit talks also dominated by North Korea and maritime disputes with China.

The call came amid international praise for Myanmar's by-elections on Sunday which gave democracy leader Aung San Suu Kyi, a Nobel laureate and former political prisoner, a seat in parliament for the first time.

Leaders of the Association of Southeast Asian Nations (ASEAN) "call for the lifting of all sanctions on Myanmar", Cambodian Secretary of State Kao Kim Hourn told reporters on the sidelines of the bloc's summit in Phnom Penh. "The lifting of sanctions would contribute positively to the democratic process and especially economic development of Myanmar," he said, quoting leaders inside the meeting room.

Myanmar President Thein Sein told reporters the polls were "held successfully", in his first public remarks on the vote.

Diplomats said the former general, who has overseen a series of dramatic reforms since taking office a year ago, told his counterparts that he accepted the result, which saw Suu Kyi's party win 43 of the 44 seats it contested. Election monitors from Cambodia, which holds ASEAN's chair in 2012, have declared the polls free and fair, and said sanctions imposed over the Myanmar military's long record of rights abuses should be lifted.

ASEAN secretary-general Surin Pitsuwan told AFP he expected the leaders to issue a formal statement on Wednesday "calling for immediate lifting of the sanctions".

Asked if sanctions should be lifted, Indonesian Foreign Minister Marty Natalegawa said: "Absolutely, yes. If not now, when?"

The by-elections are the latest sign that Myanmar's military is genuine about loosening its grip on power after four decades of brutal rule which made the country a diplomatic pariah and economic backwater.

Over the past 12 months the country's quasi-civilian government has freed hundreds of political prisoners, eased media restrictions and welcomed the opposition back into politics.

At the last ASEAN summit in November, Myanmar was rewarded for its reforms by being promised the bloc's chairmanship in 2014. It is also eager to win greater foreign investment with the prospect of sanctions being lifted.

The easing of most US sanctions would require approval in Congress, where lawmakers have welcomed changes in Myanmar but also urged caution as they seek progress on more fronts including resolving ethnic violence.

The European Union lifted some sanctions earlier this year to encourage reforms, and foreign ministers will decide the next steps when they meet on April 23 in Luxembourg.

ASEAN comprises Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand and Vietnam - a grouping of nearly 600 million people from disparate economic and political systems.

The bloc has often been dismissed as a talking shop but it has assumed new strategic importance in light of Washington's foreign policy "pivot" to Asia and the economic rise of China in recent years.

North Korea's plans to launch a rocket is also looming over the Cambodia summit, diplomats said.

Pyongyang says the launch will send a satellite into orbit but the United States and its allies have condemned it as a thinly disguised missile test.

Surin said the summit's final communique would "express a high level of concern" about the launch, which is expected to take place in mid-April.

The Philippines - which lies beneath the rocket's expected flight path - has lodged a formal protest with Pyongyang's representatives at the United Nations.

Regional tensions with China over disputed islands in the potentially resource-rich South China Sea - a vital international shipping lane - have also been discussed, diplomats said.

China has competing territorial claims in the sea with ASEAN members Brunei, Malaysia, the Philippines and Vietnam. The United States says it has a "national interest" in keeping the vital trade route open to shipping.

US ally the Philippines has been leading a push for ASEAN to present China with a binding "code of conduct" governing activities in the sea, in a bid to prevent minor incidents from escalating into major conflicts.

But Beijing is insisting it should be involved in the negotiations from the start, diplomats said.

Surin said the talks had been "given a sense of urgency" by recent clashes over fishing and exploration activity near the disputed islands in recent years.