TUNIS- Tunisia's annual inflation held steady in May at 7.7 percent year-on-year, official data showed on Thursday.

Inflation accelerated from 6.9 percent in January to 7.7 percent in April, its highest level since 1991.

The central bank raised its key interest rate to 5.75 percent in March from 5.0 percent to tackle inflation.

(Reporting By Tarek Amara Editing by Gareth Jones) ((tarek.amara@thomsonreuters.com;))