Wanda acquired the 25-storey Edificio Espana, built in the 1950s under the dictatorship of General Francisco Franco, in June 2014 for 265 million euros (now USD 292 million) and wanted to turn it into a hotel and shopping centre.
It had reportedly planned to knock down the facade, re-model the interior and build it again with the same materials, but Madrid's left-wing town hall - elected last year - refused to allow this.
The source refused to say exactly how much Baraka had offered to pay, but added that both groups had reached an agreement on the sale, which according to El Pais daily will not be finalised until September.
Both Baraka and property consultants JLL, tasked with selling the building, refused to comment when contacted by AFP.
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Wanda, owned by one of China's richest men Wang Jianlin, has been on a high-profile overseas acquisition spree in recent
Legendary Entertainment in January.
The group has also bought the organiser of Ironman extreme endurance contests, Swiss sports marketing group Infront, and a stake in Spanish football club Atletico Madrid, which reached the Champions League final this year.
It burst into the international spotlight in 2012 by buying US cinema chain AMC Entertainment for USD 2.6 billion.
Wang's group also owns more than 200 malls, shopping complexes and luxury hotels across China.