The leaders exchanged greetings and shook hands.
Putin and Merkel had a brief on-the-go conversation at the forum on Friday, too.
The Kremlin spokesman, Dmitry Peskov, has said that during their bilateral meeting, Putin and Merkel are likely to discuss holding the next meeting on the Ukrainian crisis settlement in the so-called Normandy Four format.
Earlier on Saturday, Peskov said that Putin addressed the Normandy format talks during his meeting with French President Emmanuel Macron in Osaka on Friday. Both presidents have noted the need to re-energize the talks, which include Germany, Russia, Ukraine and France.
