Models of residential buildings are seen at a sales center in Zhengzhou, Henan province, September 23, 2016. [Photo/Agencies]

BEIJING - China's Ministry of Housing and Urban-Rural Development on Monday said a group of property developers and intermediaries were investigated in a crackdown on market activities that violate rules and laws.

A total of 45 real estate developers and intermediaries across the country were investigated and punished accordingly for encouraging housing price speculation through false advertisements, spreading rumors and breaking presale rules, according to the ministry.

Housing prices in first-tier cities such as Beijing and Shanghai and neighboring second-tier cities have surged in the past few months, causing worries of a property bubble.

Eight local governments including Beijing and Tianjin have rolled out policies in the past three days to restrict speculative property buying by setting stricter qualifications and raising down payments.