"This is disturbing information about the attempted murder through poisoning against a leading Russian opposition figure," Merkel said, as quoted by the Reuters news agency.
She added: "Alexei Navalny was the victim of an attack with a chemical nerve agent of the Novichok group. This poison could be identified unequivocally in tests."
Merkel’s statement came after German doctors said at the start of last week that medical tests indicated that Navalny, a Kremlin critic who was being treated at Berlin's Charite Hospital after losing consciousness on a plane in Russia, had been poisoned.
The specific substance was not yet known at that point, according to a statement by the Berlin hospital, but long-term effects, especially to the nervous system, could not be ruled out.
The European Union last week called on Russia to investigate the suspected poisoning of Navalny and hold those responsible to account after doctors found indications of a toxic substance in his body.
Merkel said on Wednesday that Berlin expected Moscow to explain itself and that Germany would consult its NATO allies about how to respond, Reuters reported.
The EU’s foreign policy chief Josep Borrell said in a statement last week that the European Union "strongly condemns what seems to be an attempt on Mr Navalny’s life."
Navalny, a critic of Russian President Vladimir Putin, was flown to Germany for treatment after he collapsed on a flight from the Siberian city of Tomsk to Moscow two days earlier.
Moscow has denied involvement in the incident, Reuters reported.
It cited the Russian foreign ministry as saying that Germany's assertion was not backed by evidence.
Navalny, a lawyer and anti-corruption activist, has been repeatedly detained in Russia in recent years and served several prison terms for leading anti-Kremlin protests.
Novichok is the same highly toxic substance that Britain said was used against former Russian intelligence agent Sergei Skripal and his daughter Yulia in an attack in the southern English town of Salisbury in March 2018.
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Source: Reuters, IAR, PAP