The ESCA stops three brokerages from making purchases, follows suspension of 11 firms last week.
The UAE's financial markets regulator has banned three brokerages from making purchases for 15 days.
The Emirates Securities & Commodities Authority (ESCA) said in a statement the decision would affect Islamic Brokerage for Financial Services, the Emirates Islamic Shares and Bonds Centre and Al Dhafra Financial Brokers.
It gave no reason for the ban.
"We would like to inform you of the decisions from the authority chairman... to stop the companies mentioned from carrying out brokerage services for 15 days starting October 7, 2007 and ending October 21, 2007," said the statement posted on the Dubai bourse website.
"The decision is limited to prohibiting these companies from implementing or ordering any purchases while allowing them to implement and order the sale of shares belonging to the investors that have accounts with them or transferring them to another broker... or their banks."
The regulator last week suspended 11 brokerage firms for a period of one month for failing to fulfil new paid-up capital levels and bank guarantees requirements.