Christchurch residents are being warned about a man offering to wash windows, who's suspected of stealing a wallet.

Police say the man cleaned the windows at a block of flats on St Martins Road last Thursday.

They say a wallet was later stolen while someone in one of the flats was asleep.

The person’s card was used at a number of service stations in the Linwood and Aranui areas.

Inspector Richard Bruce says it's a timely reminder for people to be vigilant when people visit their home and to call police about any suspicious behaviour.