Those who look younger than 40 will now have to produce their identification cards to prove that they are aged 18 or older before they are allowed to buy cigarettes or alcohol at 7-Eleven outlets.
Counter staff will then record their birth dates in the computer system. Anyone found to be under 18 will not be allowed to buy the items.
The trial, which began last week, is part of plans by Dairy Farm Singapore, which owns more than 530 7-Eleven stores, to stop underage youngsters from obtaining cigarettes and alcohol. 7-Eleven outlets in petrol stations are not included in the trial.
Previously, 7-Eleven staff asked only those who looked under 18 to produce ID to verify their age.
Responding to queries from The Straits Times, a Dairy Farm Singapore spokesman said the trial is part of constant reviews of its "systems and processes to further enhance regulatory compliance relating to sale of age-restricted products".
She added that 7-Eleven will review and finetune the beefed-up restrictions based on feedback from the authorities and customers.
7-Eleven's latest move comes on the back of the Government's fight against rising smoking rates and tobacco addiction among the young.
The number of daily smokers among young adults aged 18 to 29 stood at 16.3 per cent in 2010, up from 12.3 per cent in 2004, according to the latest numbers available from the 2010 National Health Survey. More under-18s, who are barred from smoking, have also been caught lighting up.
This trend comes despite years of efforts to stub out smoking through measures including high tobacco taxes, public education campaigns and stricter laws. Retailers caught selling cigarettes to underage smokers will have their tobacco retail licences suspended for six months the first time; subsequent offenders will lose their licences. This comes on top of a fine of up to $5,000 for a first conviction, and up to $10,000 for subsequent convictions.