By Agence France-Presse
Addressing a 5,000-strong rally in Kuala Lumpur, Najib Razak said the Myanmar government must stop the bloody crackdown in its far west that has sent thousands of Rohingya fleeing, many with stories of rape, torture and murder.
"What's the use of Aung San Suu Kyi having a Nobel prize?" Najib asked a raucous crowd.
"We want to tell Aung San Suu Kyi, enough is enough... We must and we will defend Muslims and Islam," he said as supporters chanted "Allahu Akbar" ("God is greater").
"We want the OIC(Organisation of Islamic Cooperation) to act.
"Please do something. The UN do something. The world cannot sit and watch genocide taking place," said Najib.
More than 10,000 Rohingya have fled to Bangladesh in recent weeks, the United Nations said on Wednesday, escaping a bloody army crackdown in the north of Rakhine state.
Arrivals in Bangladesh have told AFP horrifying stories of gang rape, torture and murder at the hands of Myanmar's security forces.
Myanmar has denied allegations of abuse, but has also banned foreign journalists and independent investigators from the area.
Muslim-majority Malaysia has recently upped its criticism of Myanmar for its handling of the crisis.
Last month it summoned the Myanmar ambassador, while around 500 Malaysians and Rohingya marched to the embassy in the Malaysian capital carrying banners denouncing the "genocide."
A senior minister has called on Asean, the ten-country Southeast Asia bloc, to review Myanmar's membership, while a strongly worded statement from the foreign ministry Saturday accused Myanmar of engaging in "ethnic cleansing."
But analysts said Sunday the issue is a convenient smokescreen for Najib, who is fighting allegations he took part in the looting of billions of dollars of public cash through state fund 1MDB.
Both he and the fund deny any wrongdoing.
James Chin, director of the Asia Institute at the University of Tasmania, told AFP that Najib "is there (at the rally) to boost his standing as an Islamic leader," with a general election looming.
"Najib is looking for anything to make him look good and the Rohingya issue is simply a tool," said Bridget Welsh, a Malaysia politics expert with Turkey's Ipek University.
She added that if Najib's government really cared for the Rohingya, they would "reexamine their own treatment of the community within Malaysia."
Malaysia might be a beacon for Rohingya fleeing Myanmar but many have said they end up in a precarious and stateless limbo and suffer a new kind of marginalisation.