By Daren Butler ISTANBUL (Reuters) – Turkey said on Saturday that Twitter was biased and had been used for systematic character assassinations of Prime Minister Tayyip Erdogans government, a day after Ankaras ban on the site prompted an international outcry. However, a senior Turkish government official later told Reuters that talks with the social media company on resolving problems which led to the block were going positively. The Turkish authorities blocked Twitter late on Thursday, hours after Erdogan vowed to wipe out the social media service during the campaigning period for local elections on March 30. Leading condemnation from Western governments and rights organizations, the White House said the Twitter ban undermined democracy and free speech in Turkey.