The drugs were in the pockets of special vests worn under their outer garments. Lam and Tong, both teenagers when they were arrested, were charged with importing 1.67 kilograms and 1.47 kgs of heroin respectively.

The death penalty is mandatory in Singapore for any person found guilty of trafficking in 15 grams or more of heroin.

Judge Sinnathamby Sinnathuray rejected the defence submission that Lam and Tong had not known they were carrying heroin and that they should not be charged with importing the drug into Singapore because they were in transit.

Lam said a man approached him to carry blocks of tranquillisers to Belgium in order to avoid paying customs duties on them. He was promised HK$30,000 in payment.

He said he had not known that he would be stopping in Singapore before going to Brussels.

Lam said he first met Tong at Kai Tak Airport. But she told the court Lam was her boyfriend.

She said that in October, 1988, she applied for a passport after Lam said he wanted to take her on a holiday to Belgium. At the airport, he gave her the vest and told her to wear it. He said it was just to evade taxes.

She said she did not know what heroin looked like.

Their conviction and sentence brings the number of Hong Kong people on death row in Changi prison to nine.

An automatic appeal process means Lam and Tong could spend a year or longer on death row.

Of the seven others who have been sentenced to death, one is awaiting the outcome of an appeal while six others have had their appeals dismissed.

Three Hong Kong women are in prison awaiting trial on heroin trafficking charges.

Two were aged 17 and 19 when they were detained at the airport in 1991 while the third was arrested in last year's biggest drug bust, allegedly carrying 5.5 kilograms of heroin.