Anti-monopoly regulators fined companies including the internet giants Alibaba, Tencent, and others Wednesday in a move to tighten control of their rapidly-developing industries.

The State Administration for Market Regulation announced that 22 companies were fined 500,000 Yuan ($75,000 each) for actions such as acquiring stakes of other companies that could improperly increase their market power. Six companies belonging to Alibaba Group, five owned by Tencent Holding Ltd., two by Suning.com, Ltd., were listed as violators.

China’s leaders are concerned about the dominance of its largest internet companies. These companies are expanding into financial, healthcare, and other sensitive areas. According to the ruling Communist Party, anti-monopoly enforcement in tech is a top priority.

Alibaba has penalized 18.3 billion Yuan ($2.8 billion) for suppressing competition in April, the largest penalty ever. Others have also been reprimanded or fined for violating data protection and competition rules.

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Regulators ordered Didi Global Inc. to reform its collection and handling customer information on Sunday.