The Group of Seven foreign ministers has condemned the "confirmed poisoning" of Kremlin critic Alexei Navalny in the strongest terms, according to a statement released by the US State Department.
"We, the G7 foreign ministers of Canada, France, Germany, Italy, Japan, the United Kingdom and the United States of America and the High Representative of the European Union, are united in condemning, in the strongest possible terms, the confirmed poisoning of Alexei Navalny," said the statement.
Mr Navalny, who is being treated in a Berlin hospital, was airlifted to Germany after falling ill on a Russian domestic flight last month.
Germany says he was poisoned with a Soviet-style Novichok nerve agent in an attempt to murder him; Russia has said it has seen no evidence that Mr Navalny was poisoned.
Germany briefed the G7, which the United States is chairing this year, on its determination that Navalny "is the victim of an attack with a chemical nerve-agent of the 'Novichok' group, a substance developed by Russia," the G7 statement said.
"Any use of chemical weapons, anywhere, anytime, by anybody, under any circumstances whatsoever, is unacceptable and contravenes the international norms prohibiting the use of such weapons," the statement added, calling on Russia to establish who was responsible "for this abhorrent poisoning attack".
"We will continue to monitor closely how Russia responds to international calls for an explanation of the hideous poisoning of Mr Navalny," it said.