GENEVA (Reuters) - United Nations human rights investigators will issue their findings on the case of Kremlin critic Andrei Navalny on Monday, a U.N. statement said on Friday. The opposition politician was arrested in Moscow in January upon returning from Germany following treatment for poisoning with what many Western countries say was a military-grade nerve agent. Agnes Callamard, U.N. expert on killings, and Irene Khan, U.N. expert on freedom of opinion and expression, will issue their findings on their investigation at a Geneva press conference on Monday (1500 GMT), the U.N. said in a statement revealing the investigation.