People are being warned not to let complete strangers hug them in the street or shake their hands, after at least three people were robbed by gangs of ‘grateful people’.

In particular, older people should beware of being conned by thieves who make close contact with their victims in order to steal wallets and jewellery.

In one case a 71-year-old man was robbed after helping a motorist in a car with two women find the way to the hospital.

One of the women in the car got out and hugged him, hanging a gold chain round his neck by way of thanks. Only later did the man realise his own chain was gone, news agency ANP reported.

Most of the gangs are said to be of ‘eastern European origin’, ANP said. At least three attacks took place on Wednesday.