Bangladeshi security forces have shot dead around 130 people and arrested 13,000 in the past three weeks since the government introduced a "zero tolerance" policy against illegal drugs, the United Nations human rights chief said on Wednesday.
Prime Minister Sheikh Hasina approved the anti-narcotics campaign in early May to tackle the spread of ya ba, as methamphetamine is widely known in Asia, and worth an estimated $3 billion annually, government officials say.
UN High Commissioner for Human Rights Zeid Ra'ad al-Hussein said nobody should forfeit their rights for using or selling drugs, and he urged the government to investigate the deaths.
UN spokeswoman Ravina Shamdasani said Bangladesh's minister of law had assured Zeid there would be an investigation.
The government has previously dismissed any suggestion of extrajudicial killings and said the crackdown had popular support.
The drug is sourced from northeast Myanmar and smuggled into neighbouring Bangladesh. Bangladesh has said an influx last year of Rohingya fleeing Myanmar is partly to blame for soaring methamphetamine use. But many Rohingya say their young people are being pushed into crime because they cannot legally work or, in many cases, get access to aid.
Human rights activists are worried the Bangladesh campaign is taking a page from the Philippine drugs war, in which thousands of people have been killed in the past two years.