The UNHCR estimated that some 25,000 Rohingya and Bangladeshis boarded smugglers' boats between January and March in 2015 – almost double the number over the same period in 2014.
UNHCR spokesperson Adrian Edwards released a periodic report on the latest Irregular Maritime Movements in South-East Asia at the press briefing at the Palais des Nations in Geneva on Friday.
Referring to the recent discovery of mass graves in smugglers' camps in the southern province of Songkhla in Thailand, close to the border with Malaysia, the report said, of the trafficked people, some 300 died at sea in the first quarter of 2015 as a result of starvation, dehydration and abuse by boat crews.
One survivor who spent 62 days in such conditions compared it to a graveyard and said he lost hope of reaching the shore alive.
“The most commonly-described route has boat passengers disembarking in the Ranong area of southern Thailand, followed by a day-long road trip to the smugglers' camps towards the border with Malaysia.
“Conditions in the smugglers camps are horrific. People are held and abused until their relatives pay for their release.”
More than half the survivors interviewed by UNHCR since October reported that someone died in the smuggler's camp where they were held. Beatings are common and there are reports of rapes. Those who try to escape risk being shot.
“We heard of children being abducted off the streets or while fishing, and forced onto boats,” added the report.
The UNHCR understands that, since last October, some smugglers have abandoned onshore camps in Thailand in favour of holding passengers for ransom at sea. Once payment is made, people are taken by fishing or speed boats directly to Malaysia.
According to the NGO The Arakan Project, currently several thousand people could be held – and dozens could have already died – in these "offshore camps."
In the first three months of this year, UNHCR Malaysia saw 61 Rohingya arrivals with symptoms of beriberi caused by Vitamin B deficiency.
Considering the growing scale and severity of the boat exodus, UNHCR calls on countries in the region to work more closely together to counter the smuggling and trafficking of vulnerable people.
Regarding the much-needed efforts to crack down on this illicit trade, international law prescribes an important distinction between smugglers and traffickers involved in criminal activities on the one hand and the victims of smuggling and trafficking on the other.
The human rights watchdog also observed that law enforcement measures must also be accompanied by efforts to reduce the need for migrants and refugees to turn to smugglers in the first place, including by addressing the root causes driving people to undertake these dangerous journeys and providing safe alternatives for them to access asylum and protection.
In Myanmar's Rakhine state – where many of the smuggling victims originate – UNHCR has long advocated for and stands ready to support concerted efforts to stabilise the situation through reconciliation, the realisation of rights for all, socio-economic equality and addressing issues related to citizenship.