VIENNA (Reuters) - Austrian Chancellor Christian Kern s Social Democrats asked Facebook to disclose the identities of those behind sites which they say are spreading libel in an attempt to clean up a smear campaign scandal ahead of an election on Oct. 15. Kern has pledged to get to the bottom of his party s links to Facebook pages which have made unsusbtantiated allegations against Sebastian Kurz, the head of the main opposition People s Party, who is leading in polls for the forthcoming parliamentary vote. The scandal has already cost Kern s campaign manager his job. The Social Democrats  lawyers wrote to Facebook in Ireland on Tuesday saying the group must, according to EU rules, hand over details about users who operate sites showing potentially libellous content about Kern and Kurz.  We ... ask you to give us all information you have about the persons behind these ... pages, especially names, email-addresses, IP-addresses or other contact details,  Vienna-based law firm Freimueller/Obereder/Pilz said.  Due to the urgency of the matter we ask for your answer within four days,  the lawyers said in the letter obtained by Reuters. Facebook had no immediate comment. The Social Democrats have denied having any connection with two websites making unsubstantiated allegations against 31-year-old Foreign Minister Kurz. But Austrian media reported on Saturday that a former adviser to the Social Democrats who was dismissed this summer was originally behind the sites and that they had been kept in operation. The Social Democrats also sued the as of yet unknown operators of the Facebook pages for libel and for failing to comply with Austria s media law which forbids anonymous publishing.  ($1 = 0.8505 euros) 