Malaysian police said Monday they had found 139 grave sites and 28 abandoned detention camps used by people-smugglers and capable of housing hundreds, laying bare the grim extent of the region's migrant crisis.
Thailand, meanwhile, deployed a helicopter carrier to serve as a temporary medical and processing centre as the United States offered to launch flights to locate vessels carrying migrants but abandoned by smugglers, with rights groups warning thousands of boat people may still be at sea.
Malaysia's national police chief Khalid Abu Bakar announced the discovery of the grave sites and camps, but said it remained unclear how many bodies were buried in the inaccessible area of mountainous jungle along the Thai border.
The findings appeared to indicate a system of camps and graves larger than those discovered by Thai police in early May, a finding which ignited regional concern about human smuggling and trafficking.
The Malaysian discovery follows earlier denials by the government -- long accused by rights groups of not doing enough to stop the illicit trade -- that such grisly sites existed in the country.
"It's a very sad scene ... to us even one is serious and we have found 139," Khalid told reporters in the border town of Wang Kelian, vowing to find the culprits.
He said authorities had found 139 suspected graves and 28 detention camps, but noted that it was not known how many bodies were in each grave.
Police have released no information yet on causes of death.
- Camps holding hundreds -
Khalid said the largest of the 28 camps could hold up to 300 people, another had a capacity of 100, and the rest about 20 each.
By comparison, Thai police have said they found a half-dozen jungle camps and more than 30 bodies so far on their side.
Thailand was previously a major people-smuggling route to Malaysia, which is the preferred destination of migrants from Bangladesh and from Myanmar's oppressed Rohingya minority.
But a Thai crackdown launched after graves were found there triggered a regional crisis as nervous traffickers abandoned overloaded vessels carrying starving migrants.
After initially turning boatloads away, Malaysia and Indonesia last week bowed to international pressure to accept the boat people temporarily.
Thailand, which is hosting a May 29 regional meeting on the crisis, said Monday it had deployed a carrier to act as a "floating base with medics and police" on board.
The US said it was looking to obtain permission and support from regional governments to conduct flights to spot stricken migrant boats.
Rights groups say thousands more men, women and children may still be at sea.
Malaysian Prime Minister Najib Razak said Monday he was "deeply concerned" by the graves, vowing to "find those responsible". He said this month that Malaysia had zero tolerance for human trafficking.
But the graves will likely focus new attention on Malaysia's record in battling a bustling trade that activists say is run by criminal syndicates with the suspected involvement of corrupt officials.
- 'Modern slavery' -
The US State Department's annual human-trafficking report lists Malaysia on the lowest-possible tier, for countries which are failing to stop the trade.
"Either there has been a lack of enforcement by (Malaysian) authorities or they had closed an eye and colluded with criminal syndicates to traffick the migrants," Aegile Fernandez, of Malaysian migrant-rights group Tenaganita, said of the graves discovery.
"In today's modern slavery, traffickers cannot work alone."
Relatively prosperous Malaysia is a magnet for migrants from poorer regional neighbours.
Activists say authorities tolerate illegal migration in part to help satisfy the need for low-paid labour in Malaysian industry and agriculture.
But the State Department report says Rohingya and other migrants are often subject to abusive or exploitative work and depredations by police and other officials -- trapped in virtual slavery via debt bondage or forced into prostitution.
Khalid said Malaysian police found the jungle sites after reacting to the Thai graves discovery.
Several Malaysian villagers, however, told AFP on Monday that bedraggled Bangladeshi and Rohingya migrants had been a common sight in the area weeks before the current crisis erupted.
Some bore ugly scars or had bloodied feet, apparently from trekking across the border, and would ask locals for food and water.
"Since last month I have seen many of these migrants coming in. Every day there were around 12 to 15, sometimes even babies," said Lyza Ibrahim, a local shopkeeper.
Khalid declined to answer when asked how the extensive string of camps had been built without authorities knowing.
But Deputy Home Minister Wan Junaidi Tuanku Jaafar said the graves discovery proved Malaysia "was not hiding anything".
"Malaysia is committed and serious about resolving the issue of human trafficking," he told AFP.