Samsung Electronics rose to a record in Seoul trading a day after Fitch Ratings cut Sony and Panasonic to junk, improving the chances of the world's biggest maker of TVs to extend its dominance.

The stock rose 1.4 per cent to 1,437,000 won (€1025), its biggest five-day advance since August 1.

The shares have risen 36 per cent this year, valuing the Suwon, South Korea-based company at 212 trillion won (€151 billion), making it the 15th-biggest in the world by market capitalisation.

Sony and Panasonic, reeling from record losses, will struggle amid a strong yen and weakened economic conditions in Japan and overseas, Fitch said yesterday in downgrading the companies to junk for the first time.

Unlike Samsung, which is expanding with record spending and profits, Japanese electronics makers are shuttering factories and firing workers after struggling much of the past two decades without hit products to take on Apple, Samsung and LG Electronics.

"Samsung will benefit from the crumbling of its Japanese rivals," Kim Hyung Sik, a Seoul-based analyst at Taurus Investment and Securities, wrote in a report today.

"On top of smartphone sales, Samsung is also boosting its market share with tablet computers." Sony's rating was cut by three levels to BB-, three steps below investment grade, with a negative outlook, Fitch said.

Panasonic's was lowered two levels to BB, also with a negative outlook, the ratings company said in a separate statement.

Both companies had their short-term ratings reduced to B from F3.

Samsung is rated A+ at Fitch with a stable outlook.

Sony had 7 per cent of the global TV market in the quarter ended September 30, down from 8.4 per cent the previous quarter, according to DisplaySearch.

Panasonic dropped to 6.2 per cent from 6.8 per cent in the same period.

Samsung remained No. 1 with 25.2 per cent, according to the researcher's website.