An increase in the number of thefts today sparked a police warning to beware of sales carried out over social media channels.Police said people who had posted items for sale on social media have had their items taken without payment after they met a bogus buyer to complete the sale.A spokesman added there had also been cases where prospective buyers have their cash stolen when they turned up to collect goods.Police said that the public should avoid cash transactions and pay for items through bank transfers instead.The spokesman added that, if that was not possible, transactions should be carried out in daylight in busy areas to cut the risk of theft.He said members of the public should also make sure that they are shown proof of ownership to avoid the risk of purchase of stolen goods.