Financial ratings agency Fitch has downgraded technology giants Sony and Panasonic, marking another blow to Japan's embattled electronics sector.

The downgrades mean the firms' debt is no longer considered a safe investment.

The two companies, along with rival Sharp, accumulated billions of dollars in lost revenue last year, leading them to announce massive corporate overhauls that include selling off divisions and cutting thousands of jobs.

Fitch said Thursday it lowered Sony by three notches to a rating of BB-minus and Panasonic by two notches to BB.

Japan's technology industry faces weak demand and fierce competition from competitors such as Apple and Samsung Electronics.

Fitch is one of the three major credit rating agencies in the United States, along with Moody's and Standard and Poor's.