LONDON: European shares, set for their worst monthly performance since August 2015, opened in positive territory on Monday in a tentative rebound from a sell-off which has pushed them to a level not seen since December 2016.At 0821 GMT, the pan-European STOXX 600 was up 0.5 per cent with most bourses firmly in the black but the opening of the Paris CAC 40 was delayed due to technical issues.Sentiment remains however fragile with US stock futures trading in the red and ongoing worries about China's slowing economy previously weighing on Asian shares.The banking sector was best-performing, up 1.15 per cent with HSBC up 3.6 per cent after Europe's biggest bank by assets posted a higher-than-expected 28 per cent rise in third-quarter profit.