Beijing has announced emergency measures on July 20, under which Hong Kong, Macau and Taiwan residents as well as overseas Chinese are only allowed to purchase one apartment for self-use in Mainland, the Beijing News reported.   The new measures announced by Beijing Construction Committee are in force starting July 21. This is followed by the new measures to curb foreign investment in real estate sector that are announced on July 24.   In addition to limited purchases for Hong Kong, Macau and Taiwan residents as well as overseas Chinese, the new rules state that developers cannot sign online contracts with organizations or individuals that cannot fulfill the requirements. Otherwise, legal or economic responsibilities resulted from disagreement over such contracts are solely the responsibilities of the respective parties. Starting from July 21, those who break the rules would not have reserved registration and transaction registration completed by the official body.   According to the statistics of Centraline, a property agency headquartered in Hong Kong, Hong Kong, Macau and Taiwan residents have bought properties sized equivalent to 700000 sq. meters, which is 2.88 percent of the total amount of the apartments purchased in Beijing city. These investments totaled around 89.89 million yuan.   Experts in the industry pointed out that the new regulations can curb foreign investment to a certain extent. With the government's tightening control over the number of property that can be purchased, investment in the sector is expected to cool down.