Sept. 4 (UPI) -- The head of NATO said Friday the poison attack that sickened prominent Russian opposition leader Alexei Navalny is a "serious breach" of international law that demands a firm response.
Secretary-General Jens Stoltenberg said Germany, where Navalny is hospitalized, briefed the alliance on its findings that he was poisoned with a Novichok-class agent -- the same type of poison that nearly killed a former Russian spy and his daughter two years ago.
"There is proof beyond doubt that Mr. Navalny was poisoned using a military-grade nerve agent from the Novichok group," Stoltenberg told reporters at NATO headquarters in Belgium. "The use of such a weapon is horrific. All Allies today were united in condemning this attack.
"Time and again, we have seen opposition leaders and critics of the Russian regime attacked, and their lives threatened. Some have even been killed. So this is not just an attack on an individual, but on fundamental democratic rights.
"It is a serious breach of international law, which demands an international response."
German authorities said Wednesday they'd confirmed the poison was from the Novichok class. The agent was first developed decades ago by the former Soviet Union.
Navalny, a prominent opponent of Russian President Vladimir Putin and longtime anti-corruption activist, became sick on a flight from Siberia to Moscow last month. He was ultimately taken to Berlin for treatment and remains unconscious.
"We wish Mr. Navalny a full and speedy recovery," Stoltenberg added, saying the use of Novichok violates bans on chemical weapons.
"It is extremely important that those who are responsible are held accountable when we see this kind of horrendous use of a prohibited illegal weapon."
The NATO leader asked Moscow to cooperate fully with an impartial international investigation.
The European Council condemned the poisoning Thursday "in the strongest words possible," saying the use of chemical weapons "is completely unacceptable under any circumstances."
The Kremlin has denied responsibility for the attack against Navalny.