Barclays has been ordered to sell the Turkish unit of British insurer Aviva, sources told Reuters on Monday.Aviva mandated the bank to sell the entire unit of its Turkish non-life insurance company Aviva Sigorta."It's a pretty tough sell as they don't have a banking distribution channel, but there could be some buyers who are looking for small-medium assets," a source told the news wire, adding that the deal was not imminent.It comes after Aviva in November said it would look into strategic options for its Turkish arm. The company declined to comment on the latest reports. Aviva's shares were down 0.39% to 361.00p at 14:15 Monday.RD