Indonesia hands out severe punishments for drug smuggling and has previously executed foreigners, but has upheld a moratorium on the death sentence since 2017.

American national William Wallace Molyneaux was arrested on May 23, allegedly carrying seven packages containing 99 pills of amphetamine, Bali's narcotics agency told reporters in Denpasar. 

Molyneaux has multiple charges levelled against him including distributing drugs, which carries the maximum penalty of death by execution.

Two Kazakh men were also arrested in April with around 49 grams of crystal meth, allegedly intending to drop it off as part of a drug deal. They were accused of transacting drugs, a charge that carries the death sentence as the maximum penalty.

The American and Kazakh embassies in Jakarta did not immediately respond to AFP's requests for comment.

The narcotics agency said it had uncovered 15 drug cases in Bali between April and May, resulting in 21 arrests including five foreigners.

The other cases include an Australian man who was arrested with nearly 200 grams of hashish and 92 grams of THC in Denpasar and an Indian man caught with 488 grams of marijuana at Bali's international airport. Both face hefty prison terms.

The latest cases come after the trial of three Brits began on Tuesday, all accused of smuggling drugs or taking part in a drugs deal, leaving them also facing the death penalty.

The British embassy in Jakarta said London's policy on the death penalty was to be opposed "in all circumstances, as a matter of principle".

It said diplomats had "made representations about the use of the death penalty to the Indonesian government at the highest levels".

President Prabowo Subianto's administration has moved in recent months to repatriate several high-profile inmates, all sentenced for drug offences, back to their home countries.

According to Immigration and Corrections Ministry, more than 90 foreigners were on death row, all on drug charges.