BEIJING (Reuters) – China’s market regulator, fresh from fining e-commerce giant Alibaba $2.75 billion, said on Tuesday it had warned nearly three dozen internet “platform” companies to stop using any banned practices such as forcing vendors to use their platform exclusively.

The State Administration for Market Regulation (SAMR) said it met with 34 companies including Tencent, ByteDance and JD.com, and ordered them to conduct self-inspections within one month, with those found in violation facing “severe punishment.”

The meeting was intended to “guide” the companies in their work, according to the statement. Despite what it described as “positive” development of the platform economy in China, “harms can’t be neglected and no time can be wasted in correcting their parctice according to the law,” SAMR said.

The regulator imposed the record fine on Alibaba on Saturday.

In February, China issued new anti-monopoly guidelines targeting internet platforms that barred a range of behaviour, including forcing merchants to choose between the country’s top internet players, a long-time practice in the market.

Tuesday’s meeting was held by SAMR as well as China’s cyberspace regulator and tax administration, according to a statement on the homepage of the market regulator.

(Reporting by Tony Munroe and Sophie Yu; Editing by Kim Coghill & Simon Cameron-Moore)