The German government on Tuesday sharply condemned a nerve agent attack on a former spy that the British government has blamed on Russia, and said the perpetrators must be held accountable.

Outgoing German Foreign Minister Sigmar Gabriel said he had called British Foreign Secretary Boris Johnson to express Germany’s solidarity with the British government, and remained in close touch with British authorities.

“It’s clear the perpetrators must be held accountable. If it should be confirmed that Russia was behind (the attack), that would be a very serious incident,” Gabriel said in a statement.