Nato Secretary-General Jens Stoltenberg on Friday condemned the “appalling assassination attempt” on Russian opposition politician Alexei Navalny and called on Moscow to answer questions about the poisoning to international investigators. Mr Navalny, a Kremlin critic and corruption investigator, fell ill on a flight to Moscow on August 20 and was taken to a hospital in the Siberian city of Omsk. He has been in an induced coma in a Berlin hospital <a href="https://www.thenational.ae/world/europe/alexei-navalny-russian-dissident-flown-to-germany-after-poisoning-1.1066838">since he was flown to Germany for treatment more than a week ago</a>. German authorities have said that tests showed that he had been poisoned with a chemical nerve agent from the Novichok group. British authorities previously identified the Soviet-era Novichok as the poison used on former Russian spy Sergei Skripal and his daughter in England in 2018. "There is <a href="http://www.thenational.ae/world/europe/russian-opposition-leader-alexei-navalny-poisoned-with-novichok-1.1072103">proof beyond doubt that Mr Navalny was poisoned using a military-grade nerve agent from the Novichok group</a>. The use of such a weapon is horrific," Mr Stoltenberg said after chairing a meeting of Nato ambassadors during which Germany briefed its allies on developments. “Any use of chemical weapons shows a total disrespect for human lives and is an unacceptable breach of international norms and rules. Nato allies agree that Russia now has serious questions it must answer,” he told reporters. Mr Stoltenberg said Moscow must cooperate with the international chemical weapons organisation in “an impartial, international investigation” and provide information about its Novichok program. After the March 2018 attack on the Skripals, Nato withdrew the accreditation of seven staff members at Russia’s mission to the military alliance and rejected the applications of three others. No such action was announced on Friday. Russian authorities have appeared reluctant to investigate what caused Mr Navalny's condition, saying there had so far been no grounds for a criminal investigation. Interior Minister Vladimir Kolokoltsev said on Friday that a preliminary inquiry was ongoing but added that he saw no signs of a crime on Russian soil. Russian President Vladimir Putin’s spokesman has brushed off allegations that the Kremlin was involved in poisoning Mr Navalny and said Thursday that Germany had not provided Moscow with any evidence about the politician's condition. “We have nothing to hide,” Russian Foreign Minister Sergey Lavrov said on Friday, asserting that German authorities had stonewalled Russian requests for information. Mr Lavrov said the failure to provide information about the poisoning could indicate a lack of evidence. “Our Western partners allow themselves to make arrogant demands in such a tone that suggests that they have nothing but pathos to put on the table,” he said. The Berlin prosecutor’s office said Friday that judicial authorities in the German capital are examining a request for information from Russian law enforcement.