Japan's two biggest airlines on Wednesday grounded all their Dreamliners in the most serious blow yet to Boeing's troubled next-generation model after an ANA flight was forced into an emergency landing.

The 787 Dreamliner has suffered more than a week of bad news that has prompted investigations by aviation regulators in Japan and the United States, although Boeing insists the plane is safe.

All Nippon Airways -- the world's first carrier to receive the Dreamliner from Boeing after years of delays -- said a battery problem triggered a cockpit error message that forced the pilots to land the plane in southwestern Japan.

Both ANA and its rival Japan Airlines (JAL) -- which together are among Boeing's biggest customers for the Dreamliner -- said they would ground their entire 787 fleets pending safety checks, according to multiple media reports.

ANA has 17 Dreamliners in operation and JAL has seven.

"We recognise it is a serious incident that could lead to a serious accident," said Transport Minister Akihiro Ota said, according to national broadcaster NHK.

Ota said he was launching an investigation and had immediately dispatched aviation bureau officials.

ANA said 129 passengers and eight crew were on board the flight, which was headed from Ube in the far west to Tokyo when it diverted mid-flight to an airport in Takamatsu, on Japan's fourth largest island of Shikoku.

Police reported several "slight injuries" such as scratches after those aboard evacuated the plane via emergency chutes at Takamatsu, as several airport fire trucks deployed on the ground.

ANA would not confirm Japanese media reports that smoke was seen inside the cockpit, but one passenger was quoted by broadcaster NHK as saying he "smelled something strange" after take-off and feared the plane was going to crash.

Last week, there was a battery fire and smoke on an empty Dreamliner flight operated by JAL on the ground in the US city of Boston.

JAL said the smoke on that flight was traced to a fire from the battery used for the Dreamliner's auxiliary power unit, located in an electrical room at the rear of the plane.

"It is true that the aircraft has recently seen a series of troubles," ANA spokeswoman Naoko Yamamoto said after Wednesday's emergency landing. "But we cannot say if this has something in common with previous problems."

Another ANA official said: "During the flight (the pilots) had an error message saying 'battery problem'. We are still investigating what exactly happened," he added, without confirming the reports of smoke in the cockpit.

Boeing said it was aware of the incident in Takamatsu. "We will be working with our customers and the appropriate regulatory agencies," the company said in a statement.

The high-profile incidents over the past week are the latest issues to dog the aircraft, after production glitches delayed delivery of the first plane to ANA by three years to 2011.

ANA and JAL have a combined 100-plus planes either already delivered or on order, in deals worth billions of dollars for Boeing.

Problems bloomed last week with the fire on the JAL flight after it had landed in Boston from Tokyo. That incident was followed by a fuel leak on another JAL Dreamliner, also in Boston.

A cracked cockpit window then forced the cancellation of a Dreamliner flight in Japan before a JAL-operated plane suffered a fuel spill on Sunday at Tokyo's Narita Airport.

On Friday US regulators announced an in-depth safety review of the 787, which was followed on Monday by the announcement of a probe in Japan. But Boeing insists that it has "complete confidence" in the plane.

Considered a milestone in the aviation industry with its use of lightweight composite materials and electronics instead of aluminium and hydraulics, some 50 of the US aerospace giant's 787s are in service worldwide.

Boeing, which outsourced much of the production to Japanese and other contractors, says the plane's impressive fuel efficiency represents a revolution in aircraft design.

But questions about its safety, and the US and Japanese government reviews, have the potential to affect sales. Boeing has more than 800 Dreamliners on order.

After his ministry launched its investigation, Transport Minister Akihiro Ota said Tuesday that the Japanese people "have become enormously worried after hearing almost every day" about problems with the Dreamliner.