DUBAI, April 2 (Reuters) - Kuwait&aposs Zain ZAIN.KW has secured a $250 million four-year Islamic loan from a syndicate of three Gulf banks, the telecommunications operator said on Wednesday.Zain, which operates in eight countries in the Middle East and Africa, has signed the Murabaha sharia-compliant cost-plus-profit facility with lead lender Boubyan BankBOUK.KW , plus Kuwait International Bank K