MOSCOW (Reuters) – A Russian court on Thursday extended the custody of three lawyers for jailed Kremlin critic Alexei Navalny as they await trial on charges of belonging to an extremist group. The lawyers, Igor Sergunin, Alexei Liptser and Vadim Kobzev, are accused of using their access to Navalny to enable him to direct extremist activity from behind bars by passing materials to his supporters. Navalny has rejected that suggestion as ridiculous. When the lawyers were arrested in October, Navalny’s supporters called it an attempt to further isolate him in prison and prevent him from communicat…