They had their eyes fixed on their targets, then they walked up and pretended to bump into them.
In that split second, the pickpockets could make off with the money or wallets of their victims.
This is a common tactic used by pickpockets, some of whom work in pairs. One would distract the victim, while the other would stealthily take the victim's wallet or money.
Reminding the public to remain vigilant against pickpockets, a police spokesman said: "Members of public are also advised not to expose their cash, valuables or jewellery in public, and do not leave them unattended even if it is only for a short while."
Last year, 849 cases of theft were reported to the police, compared to 920 in 2010.
In April, two Chilean nationals were caught after stealing about $27,000 from three victims who had just come out of banks.
They threw or spat a mixture of egg and blue cheese on their victims. One of them then pretended to help the victims clean up the mess while the other took the victims' money.
The attackers were each jailed for two years.
Last December, Tan Yoke Lan, 53, was sentenced to 12 years' preventive detention for six counts of theft.
Tan would chat up elderly men, then hug or touch them before making off with their money or wallets.
In 2008, two Indian tourists pleaded guilty to picking the pockets of unsuspecting shoppers.
A 15-year-old girl and her sister-in-law, 20, had used a razor blade to slice open women's handbags to steal their purses.
The woman served four weeks in jail before she was repatriated. The teen, who had been sentenced to four months' detention in the Singapore Girls Home, was released after her appeal.
Victims of such thefts can make a police report through the Electronic Police Centre (ePC) at www.spf.gov.sg/epc/ or at any neighbourhood police centre or police post.
"They are requested to call the police immediately if they see anyone or anything suspicious," said the spokesman.
This article was first published in The New Paper.