The brokers, which include the joint ventures of Tullett Prebon, NEX International Ltd and BGC Partners, were told on Tuesday to suspend the data feed business by Chinese regulators who cited data security concerns, and the fact that the practice is beyond the scope of their licensed business, sources told Reuters on Tuesday.

Neither the money brokers nor their regulator, the China Banking and Insurance Regulatory Commission (CBIRC), have so far responded to requests for comment.

Traders said that starting on Wednesday morning, bond price quotations from the money brokers, which also include ventures of Central Tanshi and Compagnie Financiere Tradition, cannot be shown on some mainstream Chinese financial terminals, which provide information to traders.

Some vendors' platforms had blank pages where prices used to be contributed by money brokers, according to screens seen by Reuters.

Chinese bond traders have long been used to using financial platforms of data vendors such as Wind Information Co, Sumscope Information Technology Co and Dealing Matrix, so the sudden data ban sent traders scrambling to join QQ or WeChat messaging groups for price information.

"The change has made trading very inefficient," said a trader at a foreign bank. "The way other traders quote the price in the messaging groups, the price would expire before I find my counterparty."

Another trader at a foreign bank said: "I haven't been able to join any private messaging groups due to compliance issues. So the current situation feels like trading blindly."

(Reporting by Winni Zhou, Samuel Shen and Brenda Goh; Editing by Jacqueline Wong and Kim Coghill)