BEIJING, July 28 (Reuters) - China"s Ministry of Education said on Wednesday that it had begun implementing a campaign to stop paid after-school tutoring services provided by teachers working for public primary and middle schools. China issued sweeping rules last week that bar for-profit after-school tutoring in core school subjects, in an effort to boost the birth rate by lowering family living costs. The policy also restricts foreign investment in the sector. read more The ministry said in a statement on its website that it would also tackle teachers illegally receiving bribes, and show "zero tolerance" towards teachers who "teach only after classes but not during classes". The new rules threaten to decimate China"s $120 billion private tutoring industry and triggered a heavy selloff in shares of tutoring companies traded in Hong Kong and New York, including New Oriental Education & Technology Group(9901.HK)and Koolearn Technology Holding Ltd(1797.HK). Under the new rules, all institutions offering tutoring on the school curriculum will be registered as non-profit organisations. read more