Image copyright EPA Image caption Myanmar's navy with a boat said to contain mainly Bangladeshi migrants

Migrants trying to leave Bangladesh illegally are tainting the country's image, its prime minister, Sheikh Hasina, has said.

Ms Hasina said their attempts to leave had made them "mentally sick".

Describing them as fortune-seekers, she said they should be punished alongside middlemen who arrange their travel.

Bangladesh and Myanmar have seen an exodus of people fleeing south by boat through the Bay of Bengal towards Thailand, Indonesia and Malaysia.

Thousands of people - economic migrants from Bangladesh and Rohingya Muslims fleeing persecution in Myanmar - are thought to be stranded in boats.

Also on Sunday, several mass graves thought to contain bodies of migrants were found in Malaysia, authorities there said.

Trafficking networks

Ms Hasina said: "Side by side with the middlemen, punishment will have to be given to those who are moving from the country in an illegal way.

"They are tainting the image of the country in the international arena and putting their life into danger."

She said: "There is sufficient work for them; still they are leaving the country in such disastrous ways."

Media playback is unsupported on your device Media caption Jonathan Head has been investigating Thailand's human trafficking trade for six months

Ms Hasina said measures were needed to prevent migrants handing money to middlemen and "falling into a trap".

The prime minister was addressing senior labour and employment officials.

She said those trying to leave think they will "earn a huge amount of money if they go abroad", but this showed a "mentally sick" attitude.

In addition to migrants stranded at sea, thousands have landed in Malaysia, Thailand and Indonesia.

Malaysia and Indonesia have agreed to stop towing boats out to sea and will provide temporary shelter to those who have landed. Thailand has only said it would stop rejecting boats.

On Sunday, Malaysian Home Minister Zahid Hamidi was quoted by Malaysia's Star newspaper as saying graves had been found in 17 abandoned trafficking camps near Padang Besar and Wang Kelian, close to the Thai border.

He did not know how many bodies had been recovered.

Several mass graves have also been found in Thailand along a route used to smuggle Rohingyas, but these graves would the first discovered in Malaysia.

An investigation by the BBC's Jonathan Head has found entire communities in Thailand helping the traffickers.

The Thai trafficking networks, he found, bought boatloads of migrants from other smugglers and held them in the jungle until their families paid a ransom. Many migrants are believed to have perished from disease or starvation.

Asia's migrant crisis

Rohingya Muslims mainly live in Myanmar, where they have faced decades of persecution.

Rights groups say migrants feel they have "no choice" but to leave, paying people smugglers to help them.

The UN estimates more than 120,000 Rohingyas have fled in the past three years.

Traffickers usually take the migrants by sea to Thailand then overland to Malaysia.

But Thailand recently began cracking down on the migrant routes, meaning traffickers are using sea routes instead.

Why are so many Rohingya stranded at sea?

The perilous journey of a migrant boat that made it

The Indonesian villagers saving migrants