The United Nations, aid agencies and the private sector are supporting the governments of Bangladesh, India, Myanmar and Nepal where more than 25 million people have been affected by torrential monsoon rains, a UN spokesman said on Thursday.

Humanitarian colleagues also reported more than half a million people have been displaced and at least 600 people reportedly have been killed in monsoon-related incidents, said Farhan Haq, deputy spokesman for UN Secretary-General Antonio Guterres.

"In Bangladesh, it is estimated that more than 4 million people have been affected, and the UN is helping to assess needs to determine the necessary response and is also supporting the government in the areas of water and sanitation, as well as health," Haq said.

In Myanmar, water in some areas has receded, allowing some of those who had been uprooted to return home, but over 40,000 people still remain displaced, he said.