Chinese regulators fined Alibaba Group 2.8 billion dollars on Saturday over charges the online retail giant violated monopoly rules, state media reported.
China's State Administration for Market Regulation imposed the penalty after concluding the world's biggest e-commerce platform had exploited its dominant market position to punish traders who offered goods on competing platforms, in a move it said hindered competition.
Alibaba was slapped with a fine of 18.2 billion yuan (2.8 billion dollars) - which corresponds to 4 per cent of its 2019 domestic sales of some 456 billion yuan, news agency Xinhua and broadcaster CCTV reported.
With the highest-ever penalty from competition watchdogs against a Chinese internet firm come new questions about the future of Alibaba and its founder Jack Ma.
He has only rarely been seen in public since he publicly criticized China's financial oversight authority last autumn in a move that appears to have angered officials.
Alibaba said it would accept the penalty in a statement.
"We will strengthen operations in accordance with the law, further strengthen the construction of a compliance system, based on innovation and development, and better fulfill our social responsibilities," the company said.
The fine comes as the latest blow to the 56-year-old billionaire's powerful business, which has expanded its activities from online trading and financial services to areas including logistics, entertainment and tourism.
At the beginning of November, authorities halted planned initial public offering (IPO) of the company's financial subsidiary Ant Group.
It had been billed as one of the biggest IPOs of all time.
Then in December, an investigation into the Alibaba trading platform was announced.
The regulators argued in their decision that Alibaba's behaviour "eliminates and restricts competition" and negatively affects innovation and development in China's online retail platform service market. Consumer rights and interests had also been harmed, the watchdog said.
Experts say Alibaba can likely cope with the hefty fine easily. The group made a profit of more than 11 billion dollars in the last three months of last year alone.
However, the tightening up of control by the authorities does not bode well for the firm, observers noted.
