By Praveen Menon WANG KELIAN, Malaysia (Reuters) - Malaysian authorities have found 139 graves, and signs of torture, in more than two dozen squalid human trafficking camps suspected to have been used by gangs smuggling migrants across the border with Thailand, the country's police chief said on Monday. The dense jungles of southern Thailand and northern Malaysia have been a major route for smugglers bringing people to Southeast Asia by boat from Myanmar, most of them Rohingya Muslims who say they are fleeing persecution, and Bangladesh. "It's a very sad scene... To us even one is serious and we have found 139," Malaysia's Inspector General of Police Khalid Abu Bakar told reporters at a news conference in the northern state of Perlis.