Tencent’s biggest shareholder will reduce its stake in the social media and gaming giant, just over a year after promising it would not sell the stock for three years. Prosus, a spin-off by South African media and internet investment firm Naspers, said Monday it will cut its huge stake in Tencent to fund a share repurchase program. Tencent \n \n (TME)shares tumbled more than 4% on Tuesday in Hong Kong following the news. On Monday, Prosus\n \n (PROSY) and Naspers\n \n (NAPRF)’ stocks soared 16% and 23% in Amsterdam and Johannesburg, respectively. Amsterdam-based Prosus is Tencent’s biggest shareholder with a 28.8% stake worth about $128 billion. It’s not the first time Prosus has sold Tencent shares in recent years. Last April, Prosus sold a 2% stake in Tencent for $14.7 billion, the biggest block trade ever at that time. (Block trades are typically arranged directly between big institutional investors rather than on public stock exchanges.) Prosus pledged back then that it would not sell any further Tencent shares for at least the next three years. Since then, Tencent stock has dived 40%, hammered by China’s tech crackdown and a weakening economy. That crash wiped $295 billion off its market cap. Prosus said Monday that it would use the proceeds from the open-ended stock sale to buy back its own shares and those of Naspers. “It will also rebalance our asset base towards our fast growing non-Tencent assets,” Bob van Dijk, CEO of Prosus and Naspers, said in the statement. The company said that it would begin selling small numbers of Tencent shares “regularly and in an orderly manner,” but didn’t elaborate on how many. Tencent said on Monday the Prosus sale will only represent a small percentage of average daily trading volume in its stock, according to an exchange filing.