RIYADH, Oct 25 (Reuters) - Saudi Tadawul Group , the operator of Saudi Arabi's stock exchange, has given approval to 18 companies to list on the exchange, CEO Mohammed Al-Rumaih told Al Arabiya on Tuesday.

Tadawul is working on developing a market-marker for the stock exchange, Al-Rumaih added, without giving further details. (Reporting by Moataz Mohamed; Writing by Lina Najem)