MANILA -- Human Rights Watch on Thursday urged world leaders converging for annual summits in Southeast Asia to address the region's human rights crises led by the plight of Rohingya Muslims in Myanmar and what it calls the "murderous" anti-drug crackdown in the Philippines.

The call made by the US-based group, however, could run against obstacles as the hosts of the summits of the Association of Southeast Asian Nations in Manila and the Asia Pacific Economic Cooperation in Vietnam are among leaders in the crosshairs of human rights watchdogs.

The 10-nation Asean, where Myanmar, the Philippines and Vietnam are members, has a bedrock policy of non-interference in each of its members' domestic affairs, something which has been used in the past by erring governments like Myanmar's junta to parry criticisms by fellow member states.

Any leader, along with Western counterparts attending expanded summits, however, could raise controversial issues during closed-door informal sessions they call "retreats," or in one-on-one meetings on the sidelines.

Aside from rights groups, Western leaders like President Donald Trump are under pressure from other officials in their countries to press human rights concerns.

Brad Adams, Asia director of Human Rights Watch, said the crisis facing Rohingya Muslims, more than 600,000 of whom have been forced to flee from Myanmar to Bangladesh, "is among the worst human rights catastrophes in Asia in years and demands concerted global action."

"World leaders shouldn't return home from these summits without agreeing to targeted sanctions to pressure Burma to end its abuses and allow in independent observers and aid groups," Adams said. Myanmar is formerly known as Burma.

The "massacres, rape, looting, and mass burnings of homes and property" that have caused vast numbers of Rohingya to flee "amount to crimes against humanity," Human Rights Watch said, adding tougher measures were needed to press Myanmar to end abuses, acknowledge rampant rights violations and ensure the safety of displaced Muslims.

Myanmar's leader and foreign minister, Aung San Suu Kyi, will attend the Asean and Apec summits.

Her country is not a formal Apec member but she's attending at the invitation of Vietnamese President Tran Dai Quang, according to Myanmar's state-run TV. The Nobel Peace Prize laureate has faced growing international condemnation over violence against the Rohingya.

In Vietnam, Apec leaders, who are gathering there on Friday, should raise concerns about the host country's "escalating crackdown on dissidents and human rights defenders," the group said, citing the jailing of more than 100 political prisoners.

When leaders travel to Manila starting Sunday for the Asean summits, "surely someone from among the 20 world leaders at these summits can confront (Philippine President Rodrigo) Duterte about his horrific and unprecedented 'drug war' killings," Adams said. "Widespread summary executions of drug suspects are not just illegal, they are ineffectual and cruel."

Duterte denies he has a policy condoning extrajudicial killings but has openly threatened drug suspects with death. He bristles over criticism of his deadly anti-crime methods and has warned he would deal sternly with any leader who would raise human rights issues to his face.

"Lay off, that's not your business," Duterte said he would reply if the issue would be raised by Trump or others.

Concerns were also raised by Human Rights Watch over legal attacks by the government of Cambodian Prime Minister Hun Sen on the main opposition party and the jailing of opposition politicians and the Thai junta's restrictions on civil liberties.

"Thailand was once one of Asia's leading democracies, but now it is stagnating under military rule," Adams said. (AP)