DHAKA (AFP) - Bangladeshi Prime Minister Sheikh Hasina on Sunday slammed the country's economic migrants, many of whom are stranded in dire conditions at sea, calling them "mentally sick" and accusing them of hurting the country's image.

"There is sufficient work for them, still they are leaving the country in such disastrous ways," Ms Hasina was quoted as saying by the state-run Bangladesh Sangbad Sangstha news agency - her first comments on the migrant crisis in South-east Asia.

Calling the boat people "mentally sick" for fleeing in search of jobs, the premier said they "could have better lives in Bangladesh". "They are tainting Bangladesh's image in the international arena," she added.

Ms Hasina called on the authorities to halt the flow of migrants and take action against human traffickers. "Along with brokers (of trafficking), punishment will have to be given to those who are moving out of the country illegally," she was quoted as saying.

"You will have to conduct... campaigns so migrants do not give money to brokers for going abroad in illegal ways, they are falling into a trap," she reportedly told senior labour and employment ministry officials.

The region is currently battling an exodus of boat people fleeing persecution and poverty, with up to 2,000 vulnerable migrants thought to be stranded in the Bay of Bengal, many at the mercy of ruthless people smugglers.

Most are Muslim Rohingya from neighbouring Myanmar, where they are not recognised as citizens but Bangladeshis trying to escape grinding poverty are also among the migrants.

More than 3,500 migrants have swum to shore or been rescued off the coasts of Malaysia, Indonesia, Thailand and Bangladesh since the crisis erupted earlier this month.