DUBAI - Oman Telecommunication Co (Omantel) said on Monday it had agreed to buy a 12 percent stake in Kuwaiti telecommunications firm Zain in a deal that will more than double its stake.

The stake is worth about $946 million based on Zain's current market value, Thomson Reuters data showed.

In August, Omantel purchased a 9.84 percent stake in Zain for $846 million, saying the transaction was part of a strategy launched to diversify its investment and market position in the region.

On Monday, Omantel said it had signed a non-binding letter of intent with Kuwait-based Al Khair, an investment vehicle of Kuwait's Al Kharafi merchant family, to purchase its 12 percent stake in Zain.

Al Khair is studying and evaluating the offer, the statement said, without providing the price.

The biggest shareholder in Zain is the Kuwait Investment Authority sovereign wealth fund with over 24 percent, Thomson Reuters data showed.

(Reporting by Saeed Azhar; editing by Jason Neely; Editing by Andrew Torchia) ((Saeed.Azhar@thomsonreuters.com; +971 44536787; Reuters Messaging: saeed.azhar.reuters.com@reuters.net))