Japan's biggest telecoms firm, NTT, has racked up the worst losses ever recorded by a non-financial Japanese firm.

The group lost of 812bn yen ($6.4bn; �4.4bn) in the year which ended in March.

The loss was widely expected after the company issued a warning in April, more than doubling previous loss estimates.

The high-profile telecoms group has invested heavily in increasing its global reach, and promoting its i-mode mobile phone - which allows users to surf the internet - in Asia and Europe.

But the expansion has yet to pay off, and the group booked a loss of 1,400bn yen on overseas investments.

While the i-mode marketing drive represents recent promotion, much of the investment was made during the height of the technology boom which inflated the price of telecoms and internet firms.

'Aberration'

With the losses out of the way, the group has predicted a return to profit in the current financial year.

"Last year was an aberration," said outgoing President Junichiro Miyazu, who will be replaced by Norio Wada next month.

But Mr Miyazu was hesitant about making further forecasts about the future of the industry.

"Since new factors emerge every year it's very hard to make predictions because the pace of change is so fast in the industry," he said.

Mobile shipments from Japan fell 50% in March.

And NTT DoCoMo's third generation (3G) services - which offer mobile users faster internet access and colour screens - is failing to prove as successful as rival services.

KDDI, Japan's second largest mobile phone firm, launched 3G last month and has already attracted three times more subscribers than NTT DoCoMo has signed up in seven months.