The Saudi bourse regulator has fined four listed firms for breaching disclosure rules as it tries to polish the image of an opaque bourse gradually opening up to foreign investors.

The chief executive of Zain Saudi Arabia, the kingdom's newest mobile phone operator affiliated to Kuwait's Zain, was fined SR50,000 ($13,333) for disclosing at a press conference the possibility of a capital hike, the Capital Market Authority (CMA) said in a statement.

The chief executive of Anaam International Holding Group was also fined SR50,000 for disclosing to the media information about the firm's first-quarter earnings, CMA said without elaborating.

Filling and Packing Materials Manufacturing and Arabian Pipes were fined respectively SR200,000 and SR100,000 for not disclosing on time a recommendation by their boards not to distribute any dividend for 2009, CMA added.

Like others in the Gulf region, Saudi Arabia's stock exchange has been dogged by allegations it is opaque and subject to manipulation of stock prices, and the regulator has slapped hefty fines on investors and executives for violations.

The bourse is gradually opening up to direct foreign ownership amid tough competition from regional bourses. Over the past two years, CMA has stepped up efforts to clamp down on irregularities, even imposing one jail sentence and revoking the licences of several brokerage firms for violations.-Reuters