"A coordination meeting [of P5+1] took place, as well as a bilateral Russian-Chinese meeting," the source said.
The P5+1 group, comprising Russia, the United States, China, the United Kingdom, France and Germany, is meeting in the Austrian capital to discuss Iran's nuclear program, as another round of talks with Tehran is taking place.
Russian Deputy Foreign Minister Sergei Ryabkov said Tuesday that the P5+1 group would try to use this round of talks to work out a mechanism of easing anti-Iran sanctions.
The P5+1 states and Iran are working toward the end-of-June deadline to reach a final deal ensuring the peaceful nature of Iran's nuclear energy program.
In April, Iran and the P5+1 group worked out a political framework agreement on the Iranian nuclear program in the Swiss city of Lausanne. Under the deal, Tehran pledged to cut back its uranium enrichment and decrease the number of centrifuges in the country, in exchange for gradual lifting of international sanctions imposed on the Islamic republic.