In the past two weeks, nearly 3,000 people from Myanmar and Bangladesh have been rescued or swum to shore in Malaysia, Indonesia and Thailand.
"I continue to follow with profound worry and pain in my heart the stories of many refugees in the Bay of Bengal and the Andaman Sea," Francis said to crowds attending his Pentecost Sunday address in St. Peter's Square in the Vatican.
The migrant crisis in Southeast Asia is being blamed on Rohingya Muslims fleeing persecution in Myanmar and Bangladeshis trying to escape poverty at home become prey to human traffickers.
According to Reuters, after Thailand cracked down on the practice, traffickers began abandoning overloaded boats on the open sea rather than trying to smuggle the people through Thailand. The United Nations refugee agency said on Friday some 3,500 are stranded.
Francis said he welcomed efforts by countries that have agreed to take in people who are facing "severe suffering and danger", but encouraged "the international community to offer them humanitarian assistance".
Malaysia has pledged assistance and ordered the navy to rescue thousands adrift at sea. Malaysia and Indonesia offered to allow the migrants to come on shore temporarily but Thailand has ruled out migrant assistance.