The North Atlantic Council will meet on Friday, with Secretary General Jens Stoltenberg to address the media afterwards.

German officials will brief the other 29 allies, after Berlin announced there was "unequivocal evidence" the 44-year-old Kremlin critic had been poisoned with the nerve agent.

Novichok was the substance used against Russian ex-double agent Sergei Skripal and his daughter in the English town of Salisbury two years ago.

The Skripal case -- the first use of offensive use of chemical weapons in Europe since World War II -- prompted NATO to expel seven Russian diplomats in retaliation.

The Navalny poisoning, the latest in a long series of assassination attempts against Kremlin critics, has triggered international outrage and demands for punitive measures against Moscow.